CHAPTER VITHE POSSIBILITY OF DEFEATING THE SUBMARINEIn the present European war, for the first time in the world's history, the submarine, as is also the case with the airplane, has taken an important active part, and has become a weapon of unlimited value. We have seen that even as early as the war of the American Revolution the submarine was utilized, but up to modern days the submarine had never been a really significant or consequential factor in naval warfare; its use had been previously but sporadic and experimental. In the wars of the past it had no bearing upon the destinies of nations or the outcome of naval battles. To-day the situation is very different: the submarine has been called into action as a weapon of primary value and is producing tremendous results.In the conflict in which we are now engaged the destructive capabilities of the submarine have been made use of, for the most part, in the work of commerce destruction and in the task of hampering communication by sea. It has not taken a great deal of active part in actual naval battles, although on some occasions its presence has been severely felt by the fleets of its enemies. But the submarine has been an important factor in naval warfare by reason of the fact that its very presence and the possibility of its use have checked the actions of belligerent fleets of battleships in no inconsiderable way. In writing of this I am reminded of the fact that a short time ago I was introduced to a pleasant-faced,motherly old lady who, when she learned that I was an inventor of submarine boats, exclaimed, "Why! I should not think you could sleep nights from thinking of all those poor people who have been drowned by the U-boats!"I asked the old lady if she had ever considered the submarine from another angle of view—viz., as a life and property saver in the present war—and she said, "No; how could that be possible?" I then explained to her that had it not been for the existence of the submarines many more lives would have been sacrificed than have been lost by the use of submarines. I asked her to consider what would have been the loss of life if the battleships, cruisers, gunboats, destroyers, etc., had met on the high seas and fought as they were intended to fight. A submarine carries a crew of but a few men, while a battleship may carry a thousand, consequently thousands of men would have been killed in the old-time methods of fighting, compared with the few that have been killed in the submarine warfare. Then again, had it not been for the submarines lying off Russia's, Germany's, England's, France's, Italy's, Austria's, and even Turkey's shores, many seacoast cities, towns, and hamlets would undoubtedly have been bombarded and destroyed, and countless thousands of lives and enormous property valuations lost forever to the world; for one must remember that a life, or a property once erected by hands that are gone, if lost, can never be economically replaced. The only reason such bombardments have not occurred is the fleet commander's fear of that waiting, watching invisible sentinel, the submarine, which lies off the respective combatants' shores; and thus because of its existence thousands of lives and great property valuations have been saved. Thus, while thesubmarine has not been much of a fighter in naval battles, it has, in my opinion, been of great power as a preventer of fighting, and that, after all, is rather more in its favor than against it.It is, however, the submarine in the role of commerce destroyer which is attracting attention at the present time. The democratic nations of the world are face to face with the problem of transporting men, food, ammunition, and supplies to Europe. The submarine threatens to cut off communication between Europe and the other continents. It is very necessary that means be taken to offset the activities of the submarine. It is this problem which leads me to write upon this topic.BRITISH SUBMARINE C-2 ARRIVING AT PORTSMOUTH IN A GALENote hydroplanes at centre of conning tower; in later types these were placed under the water, as they were found ineffective in this positionThe devices which have been proposed for capturing and destroying the U-boats in order that navigation upon the Atlantic Ocean may be made safe have run into the thousands. I have had hundreds of impractical schemes sent to me, and the Navy Department and the Naval Consulting Board have been almost swamped by the various suggestions that have been pouring in from all over the country in response to editorials in the newspapers to "Save us from the U-boat!"; "American inventors, rise in your might and strike down this peril which works unseen, like an assassin in the dark!" etc. The devices proposed run all the way from blowing up the whole restricted area or war zone of the ocean to fishing for submarines from aeroplanes, which latter method offers a good chance for sport, at least; and if the submarine designers and commanders were asleep the fishermen might have a good chance of making a catch. Many of my engineering friends with whom I have discussed the U-boat problem have urged upon me that I ought, inorder to save the time, energy, and money of many earnest and patriotic—but misinformed—citizens, to publish some material showing the fallacies in many of these schemes which apparently are so promising, and at the same time to point out wherein some have value, and along what lines I believe success to be attainable.At the beginning of the war I myself sent to the Navy Department a number of devices for detecting the presence of and destroying submarines in shoal waters, some of which may have already been known to the Navy Department, and several of which I have since seen published as being the ideas of others; this goes to show that where many minds are working toward the solution of any particular problem several are likely to arrive at the same point. In the interest of public policy I do not think that any device hitherto unknown which offers a chance of success if used against an enemy U-boat should be described, and therefore I should not describe any such device if such were known, but shall limit my remarks to a discussion of some of the devices that have been proposed and described publicly. Trying to serve the country by developing a certain idea, when that idea is itself old or impractical, is evidently a waste of mental energy and money. Further, to show how some of these methods of attack may be offset by the submarine commanders will also serve to prevent the country from relying on false defences; the submarine is a real menace, and should not be lightly regarded. I hope to impress upon people that this is a very serious proposition. It is a problem which should and does attract the leading minds of the mechanical world; and it is not to be coped with by any fanciful notions. While the devices proposed thus farare individually very numerous, they may be classified into a few distinct categories. I would designate them as follows:Offensive Devices:I. Airplanes and dirigibles for the location and destruction of submarines.(a) By bomb attacks.(b) By directing surface boats to the attack of sub-vessels.II. Offensive appliances for use of surface vessels:Sound detectors.Submerged mines operated from shore stations.Deck guns.Under-water guns.Aerial torpedoes.Searchlights.Echo devices.Magnetic devices for locating and destroying submarines.III. Channel and open-sea nets.IV. Submarine vs. submarine.Defensive Devices:I. To be installed on surface vessels to baffle and elude submarines:Sound detectors (spoken of above).Blinding searchlights.Blinding apparatus.II. To offset torpedo attack:Nets.Plates.Magnets.Bombs.Discs.III. Unsinkable ships.IV. Tactics to elude the submarine:Convoying a merchant fleet.Zigzag course.Smoke screen.Cargo submarine.High speed.In considering the practicability or value of these devices, we must first consider the capabilities of the submarine and the proper tactics for her commander to pursue. In a paper read before the Institution of Naval Architects in London, in 1905, I described, illustrated by diagrams, the proper method to be pursued in attacking a surface ship, in which I contended that the commander of a submarine, on sighting an enemy, should always keep the hull of his own boat below the horizon in its relation to the enemy vessel, and try to intercept the approaching vessel by taking frequent observations of her course and speed. When the two vessels approach sufficiently near to make it possible for the larger surface vessel to observe the smaller submarine (the comparative range of visibility being proportionate to the exposed surfaces of the two vessels above the horizon), the submarine should then entirely submerge, with her telescopic periscope withdrawn below the surface of the water to avoid the making of a "wake"—which looks like a white streak on the water. When the commander wishes to make an observation he should first bring his submarine to restand then extend the periscope above the surface for a brief instant only, and thus avoid the chance of being seen. Earlier in the war it was common to detect the submarine by her wake, but now, since the fitting of merchantmen with guns, the above tactics are usually pursued, and the first intimation the crew has of the presence of the submarine is the shock of the explosion caused by the torpedo "striking home."GERMANY'S U-9 AND SOME OF HER SISTER SUBMARINESAEROPLANE AND SUBMARINE(Drawing by T. E. Lake.)For defense of coast lines aeroplanes and submarines may work in conjunction. Aeroplanes, with their enormous range and high speed can locate surface ships many miles away, beyond the range of a submarine's periscope or sound-detecting devices. It could then direct the submarine by wireless or direct communication. Aeroplanes, however, are of great danger to enemy submarines. Flying at certain altitudes they can see submarines a short distance below the water and swoop down on them, dropping depth bombs or trailing torpedoes.Aeroplanes and Dirigibles.—These are undoubtedly valuable near land in shallow water,providingthe water is clear and has a bottom in striking contrast to the hull of the submarine. I should consider the dirigible likely to prove of more value than the aeroplane, owing to its ability to hover directly over and regulate its speed to that of the submarine and thus enable itself to drop depth bombs more accurately. Experience has shown that it is almost impossible to calculate where a bomb will strike when dropped from a swiftly moving aeroplane. The chance of its striking the submarine would be very slight. The use of aeroplanes has, however, forced the submarines away from shoal clear water and probably has been instrumental, also, in causing them to become equipped with high-angle rapid-firing guns. In a battle between swiftly moving aeroplanes and submarines with high-powered guns firing shrapnel, the chances are nearly all in favor of the submarine, as they can carry the most powerful guns and are firing from a much more stable platform; in fact, the best analogy I can think of is that of a gunner in a "blind" firing at a flock of ducks passing overhead. Aeroplanes have been used, however, as scouts, merely to detect a submarine and direct surface ships to the attack; also, aeroplanes have directed trawlers to a submarinelying submerged at a shallow depth. This method of attack has undoubtedly been successful in some instances, but where success might have been met with in this manner with the earlier submarine boats, which were not provided with guns, it is now a problem easily met by submarine architects. Submarine boats may be built which have no fear of this combination. One of my earliest designs provided for a revolving armored turret to carry heavy-calibre guns; this revolvable armored turret would extend only above the surface and would carry guns of sufficient calibre to sink any trawler, destroyer, or other craft except an armored ship. It has recently been reported that the Germans are bringing out ships fitted with turrets of this type, and as they are familiar with my designs from the Patent Office specifications, and also have my working drawings of a large cruiser submarine mounted with guns, in 1905, I have no doubt that the report is true, as they have consistently been the first to adopt such new devices as may be needed to offset any attack against their submarines, or to increase their means of offence against surface craft without relying upon torpedoes alone. As far back as 1902 theProtectorwas fitted with a small gun on top of her conning tower, with the breech extended into the sighting hood and a tampon controlled from within the turret for closing the muzzle, so that no water would enter the barrel when the vessel was submerged, thus permitting a new cartridge and shell to be inserted into the breech when submerged; then, by momentarily bringing the conning tower above the surface, we could fire, then submerge and reload, rest and fire again, etc., thus providing a disappearing gun on a very stable platform.In deep water the submarine may readily escape detection by aeroplanes by sinking below the depth to which vision can penetrate. This depends upon the amount of foreign substance held in suspension in the water. Along the Atlantic coast it is possible to see only a few feet; as you go off shore vision becomes clearer, and it would probably vary during the dry seasons from four to five feet near shore to forty or fifty feet well off shore. The greatest distance I was ever able to see in my experiments in the Chesapeake Bay with a powerful searchlight was forty feet. In Long Island Sound one can seldom see over fifteen feet, and after storms, when sediment is carried into the Sound, sometimes it is difficult to see over three or four feet. I have been down on muddy bottom at a depth of one hundred feet and could not see my hand held close to my face. At a depth of one hundred and twenty-five feet in the Baltic on sandy bottom I was able to see twenty-five feet. This was about eight miles off shore, opposite Libau, Russia. In the English Channel the frequent storms stir up so much sediment that it is seldom possible to see over fifteen feet, while in the Mediterranean and our Southern waters near the Florida coast, near Nassau, and in the Caribbean Sea, it is possible at times to see seventy-five or even one hundred feet. Now there are means available to the submarine to enable it to lie at rest submerged at depths exceeding one hundred feet, and yet have a full view of surface ships and also to scan the heavens, therefore I would say that aeroplanes and dirigibles will prove ineffective against submarines fitted with revolvable turrets, high-angle firing guns, or where they may be operating in clear water exceeding one hundred feet in depth or in shallow water where the sediment held insuspension is in sufficient quantity to prevent discovery. Aviators with whom I have discussed this problem tell me they can seldom detect objects lying on the bottom, even in comparatively shallow water.RUSSIAN CRUISER-LAKE TYPE SUBMARINE IN SHED BUILT BY PETER THE GREAT—1905This was the first large submarine of the cruiser type, built substantially after the design submitted by the author to the U. S. Navy in 1901.Sound Detectors.—We have heard many claims put forth concerning the great results which were to be attained in fighting the U-boat by the use of various sound-receiving devices in the nature of microphones, in detecting the presence of submarines by hearing the hum of the motors and the noise of their machinery. These devices are proposed both for offensive and defensive purposes. A vessel equipped with such mechanism is believed to be able to escape upon hearing a U-boat, or to seek out the submarine and destroy it. Those who have been expecting so much from this source are probably not aware of the fact that submarine inventors themselves were the first to utilize this method of sound detection under water to enable them to apprehend the presence of other vessels in their vicinity before coming to the surface; they have made use of such devices for years.I well remember my first long submergence of ten hours' duration down at Hampton Roads, near the mouth of the Chesapeake Bay, July 28, 1898. During this period of submergence the machinery was shut down for a time, and one of the first sensations we experienced was the strange sounds which came to us of the propellers and paddle-wheels of surface vessels passing in our vicinity. The first vessel that we heard was a tugboat; we could tell that by the sound of her puffing exhaust and the characteristic sound of her machinery. We thought at first she was coming right over where we were submerged, and feared she might carry away our masts, which extended above the surface, but she passedon, and then we heard coming at a distance the uneven and characteristic sound of a paddle-wheel steamer as her paddles slapped the surface of the water. Then we heard the slow, heavy pound of an ocean liner coming in, and knew that she had a loose crank-pin or cross-head bearing by the pound every time the crank-pin passed over the dead centre of its shaft. The click, click of the little high-speed launch was also easily detected—all this without any sound receiver on the vessel. Any of us simply sitting or standing anywhere in the submarine could hear outside sounds. By putting the head of an iron bolt against the skin of the ship and sticking the end of the bolt in my ear the sound was much intensified, as the whole steel fabric of the ship became a great sound collector. This led me to make experiments toward determining the direction of the sounds under water, and I applied for a patent on a device which could be swung in different directions, on the theory that the sound waves would be stronger when coming straight from their source, but shortly after this the experiments of Professor Gray and Messrs. Munday and Millett were published and I dropped my application and did nothing further in the matter, as they seemed to have solved the question in a satisfactory manner. Afterward Professor Fessenden brought out his oscillator and improved sound detector, with which it is possible for submarines to carry on wireless conversations under water when at a distance of several hundred feet apart, and to pick up the characteristic sounds of different types of surface ships at considerable distances. Sound detectors are of greater benefit to submarines lying in wait for their enemies than they are to surface vessels, as they enable the submarine to lie at rest, submerged and invisible, herself giving no betrayingsound, while no surface ship can come within the zone of her receiving apparatus without betraying its presence.Submerged Sound Detectors.—It has been stated that sound detectors connected to shore stations have been able to detect submarines when passing in their vicinity, and, by the triangulation method as applied to the intensity of sounds, observers have been able to tell approximately the location of the U-boat from the sound of the U-boat's machinery. The obvious thing for submarine designers and commanders to do to offset this danger to the submarine is to use noiseless machinery in the U-boats, or to send other U-boats with a wire-cutting grapnel to cut the shore connections of the sound transmitter. It is apparent that this method of attack is applicable only to points close to shore or in places like the English Channel.A GROUP OF GERMAN U-BOATSNote their broad decks, due to buoyant superstructure.RUSSIAN-LAKE TYPE CRUISING SUBMARINE "KAIMAN" MAKING A SURFACE RUN IN ROUGH WEATHER IN THE GULF OF FINLANDDeck Guns.—The mounting of deck guns on merchantmen for defence against the submarine has proved of slight value. When it was first proposed to mount guns on American merchant ships I wrote the Navy Department on March 11, 1917, in part as follows: "I have tried, in the interest of this country, to impress this fact upon the people (that the submarine, because it is invisible, is invincible), but I find in talking with many intelligent people, that they do not and cannot comprehend the possibilities of the submarine when it is taken seriously and the effort is made to get all there is out of it, without reference to political, financial, or prejudiced interests. Thedestructivenessof the submarine is growing; devices which were effective in detecting and trapping submarines early in the war are now becoming useless. The theory that putting a gun on a merchant ship is going to protect that ship, her crew and passengers, will,I fear, be equal to the signing of the death-warrant of all that are on that ship if we are at war, as the slogan in to-day's headlines (as per copy clipping enclosed)—'Sink any ship you see'—will be met, I fear, by a German slogan of 'Sink every ship you meet, but don't let themsee youdo it.'"Since that time many ships fully equipped with arms have been sunk by torpedoes and have never seen the submarines which destroyed them. There is no way to attack submarines by gun fire unless they are seen, and commanders of submarines are becoming expert in concealing their presence.Submarine Guns, Aerial Torpedoes, Searchlights.—For an under-water gun to be effective, there must first be discovered some way to locate the target; this, of course, is almost impossible. Aerial torpedoes or depth bombs might be effective if the submarine were seen, but it is the business of the submarine commander to keep out of sight. Powerful searchlights have very little chance of picking up the periscope or conning tower of a submarine. I remember lying all one night in theArgonaut, during a storm, at the outer edge of the mine fields off Fortress Monroe, at the time the whole country was in dread of an invasion by Cervera's fleet during the Spanish-American War. We were in forbidden territory, having been delayed by the storm in getting into harbor before "Curfew" rang, so to speak. The powerful searchlights of Fortress Monroe were playing all night, but they did not detect our presence, as only our sighting hood was above water, and presented such a small object, and being painted white, it was not distinguished from the "white caps" on top of the sea caused by the storm.Searchlights under water are useless because of the particles of foreign matter held in suspension which reflect backthe glare of the light. TheArgonautwas fitted with powerful searchlights and reflectors located in her extreme bow, with a pilot-house or lookout just above the three searchlight windows. The greatest distance we were ever able to see was during some night experiments in the Chesapeake Bay during a long dry spell, when the sediment had had an opportunity to settle, and that was only forty feet. The light would penetrate through the water several hundred feet and make a glow on the surface, but vision could not penetrate the water. For instance, it is said that after a storm a glass of Mississippi River water will show fully an inch of sediment. To see through three or four inches of that kind of water, therefore, one must see through an inch of mud. It is well known that no light has yet been found that will enable vision to penetrate through a heavy fog, due to the reflection of light upon the minute crystals of water held in suspension in the air. It appears hopeless, therefore, to expect vision to locate submarines by seeing through the opaque substance held in suspension in all water.Echo and Magnetic Devices.—Locating submarines by echo has been proposed, but apparently without thought as to what would happen to the vessel giving out the sound in the effort to get an echo back from a submerged submarine, lying in wait with her "ears" waiting to hear some suspicious sound. Also, magnetic devices for the purpose of detecting submarines, if ever found practical, will probably be kept so busy leading their operators to and investigating large steel ships that have already been sunk by submarines that they will probably miss the little submarine, which can easily sink them while they are investigating these other sunken ships.Channel and Open-sea Nets.—These have been and are being used with some success, but that success has been attained only because at the beginning of the war the submarines had no means for determining the presence of the nets before becoming entangled in their meshes, and when they once became entangled they had no means to cut themselves loose. Devices are now available which enable the commander of a submarine to locate a net before reaching it, and to destroy that net and all its attached mines with but little danger to his own vessel. To what extent these devices are being used is unknown. However, when the submarine is not especially fitted for the detection and destruction of nets and attached mines, they are probably the most efficient type of trap yet provided for capturing and destroying these "submarine devil fish." TheScientific Americanpublished an article by me in 1915 describing a submarine fitted with mine-evading devices and meant to under-run nets, which has been reproduced in the previous chapter.THE U-65Photograph copyright by Underwood & UnderwoodOne of the large German U-boats fitted with deck guns hailing a Spanish merchantman which they have held up.RUSSIAN-LAKE TYPEThese vessels are powerfully armed, fitted with four torpedo tubes firing fore and aft, also Dzrewiecke apparatus for firing torpedoes to either broadside.The above articles having been published previous to our country entering the war, and being thus of public knowledge, it is permissible to republish them as a method which might be used to advantage in preventing the German submarines from coming out from their bases. It is admitted that the allied fleets are overwhelmingly superior to the German fleet, yet they are impotent to attack the German battle fleet or to make reprisals on Germany for the constant depletion of their merchant fleet, because Germany's fleet of battleships, cruisers, and merchantmen will not come out in the open, but lies safe behind nets and mine fields as their inner defence, using her submarines on her outer line ofdefence. As mentioned, Winston Churchill said we must "dig them out like rats out of a hole." That was over three years ago, but not one has been dug out as yet, and, although it would be a very expensive process to do so, it might be possible, by the coöperation of submarines, surface ships, trawlers, and aeroplanes, to move forward gradually and expansively a double or treble line of nets and to defend such a line of nets just outside of the range of the most powerful shore-defence guns. The battleships should be protected by operating between the line of nets to prevent attack upon them by submarines in the rear. Bottom-working submarines would be needed to clear away the mines and nets of the enemy as the mines and nets were moved forward. Constant patrol and repair of the nets would be maintained under the guns of the net-protected fleet, and allied submarines must be on constant attendance in advance of the first line of nets to meet the concerted attack of a portion of the German fleet in "rushing" the line—which must be expected in the attempt to break the same—in order to let out a fleet of their submarines into the open sea to continue their attacks on the allied and neutral commerce of the world. This seems to me the only practical way of stopping up the hole or holes through which the German submarines come out, and to make it effective it would require a double line of nets and patrol fleets extending from Norway to Scotland, and across the English Channel, and across the entrance to the Dardanelles from Brindisi, Italy, to the Albanian coast. Also, battleships which should be unsinkable and provided with longer-range guns than those of the enemy would be required. Perhaps the combined navies of the world as arrayed against the Central Powers could accomplish it, butunless their guns were more powerful and far-reaching than the shore guns, even then they could not land an invading army.Submarines vs. Submarines.—Submarines to search for and sink other submarines have been proposed in all sorts of forms and advocated in the press under various titles, such as the "Bloodhounds of the Sea" and other fantastic and sensational captions. Submarines cannot fight submarines, because they cannot see each other, and if they are fitted with noiseless machinery they cannot hear each other. Therefore one might put thousands of submarines in the great ocean, and so long as they kept submerged the chance of their ever finding or colliding with one another would probably be not once in a year.Derelicts have been known to keep afloat on the ocean for years, although constantly searched for as a menace to navigation. Here the searchers have had sight to aid them, and the object of their search has floated on one plane, the surface of the water, while submarines may navigate or remain at rest at various planes up to a depth of about two hundred feet, which is equivalent to multiplying the area of the ocean to be searched several times, and that in darkness, without the aid of sight to assist. It is ridiculous to think that anything can be accomplished except by the merest chance by one submarine searching for another.Our attention will now turn to consideration of devices of the second class; namely, those which have been offered as a means of defence against the submarine.Blinding Searchlight; Blinding Apparatus.—Blinding deviceshave been proposed which aim to direct powerful searchlights against the periscope so as to blind the commander.These are schemes based on very false notions. Submarine commanders frequently have to con their ship against the sun's rays, and have colored glasses to enable them to withstand the intensity of the sun's rays, so that it would be impossible to blind them this way. Further, I cannot imagine a more desirable target for a commander to direct his torpedoes against than a bright spot, either on the surface or submerged, as he knows the searchlight is probably on what he wants to hit; it becomes an illuminated bull's-eye for his target. Again, it has been proposed to blind the periscope by putting a film of oil on the surface to obscure the object glass of the periscope when it emerges through this oil, and a member of one of the British commissions told me he knew of shiploads of oil being pumped overboard, possibly for this purpose, or to show the course of a periscope through its "slick." Some periscopes have been built with means for squirting alcohol, gasoline, or other substances to clear the object glass if ice or salt forms on it. A device of this kind would clear off the oil.Nets; Plates.—There have been many devices proposed for warding off the torpedoes, the usual weapon of the submarine. The most common of these schemes designate the use of nets or plates suspended from booms carried out from the sides of the ship and extending down into the water. Any device of this kind seriously handicaps the ship's speed, and, if she is once sighted by a submarine, is almost sure to be come up with and attacked. Plates, to be effective against a broadside attack, would need to be the full length and extend to the full depth of the ship. Now, skin friction of a ship's plating is the principal resistance to be overcome in forcing a ship through the water up to speeds of aboutten knots, the average speed of the cargo-carrying ship. If you increase the speed beyond ten knots, other resistances come more prominently into effect, such as wave-making resistance, etc. Now a ship afloat has two sides, while a plate suspended in the water equal to the length and depth of the ship also must have two sides, and thus presents nearly the same square feet of plate surface to the friction of the passing waters as the two sides of the ship, and two plates, one on each side, present nearly twice the area and thus very materially reduce the speed. This resistance is further augmented by the roll and pitch of the vessel, and in a severe storm the plates would be unmanageable and of great danger to the ship itself. The resistance of nets with its vertical members is much greater than that of plates. To get some idea of what the resistance of a vertical rod extending down into the water is, take a broom handle and attempt to hold it vertical when it is extended down into the water from a launch running at about ten knots; it is almost impossible to hold it. A net with a mesh fine enough to catch a torpedo would consist of thousands of vertical members as well as horizontal members extending down into the water.I have been informed by one naval architect of standing who investigated this phase of the problem that nets of sufficient strength to protect the sides of a ten-knot ship from a torpedo attack cut the speed of the ship from ten knots down to two and one-half knots per hour. It would therefore take a ship protected in this way four times as long to make her voyage; her chance of discovery would therefore be four times as great and her chance of destruction, if once discovered, be almost certain, as a submarinecould readily overtake her and plant mines in her course or even tow a mine underneath her bottom and explode it there, which would destroy the ship much more completely and quickly than a Whitehead torpedo exploded against her side. Devices have also been developed which enable a torpedo to dive under a net and explode under a ship's bottom by a slightly delayed detonator.Torpedoes have also been built with net-cutting devices, and they have been known to penetrate a ship's plating and sink the vessel without exploding. It is not an easy matter to stop a projectile weighing nearly a ton speeding at thirty-five or forty miles an hour. I can see no hope in stopping the submarine menace by any device in this class.Magnets.—Some proposals have been made to divert the torpedo by powerful magnets extended out beyond the sides of the ship or at the ends—on the theory, I suppose, of fishing for little fish in a pan of water—the Whitehead torpedo being built of steel in this country and England. It is not generally known that the Schwartzkopf torpedo built by the Germans is built of bronze, or at least it was when I went through their works in Berlin several years ago. Even were it of steel, I doubt if a magnet could be built powerful enough to attract or divert a Whitehead steel torpedo from its course unless it passed very close to the magnet, as any artificially erected magnetic force diminishes in strength very rapidly as the distance from the object is increased. Recall, for instance, the powerful magnets used in handling scrap and pig iron; while they will lift pigs or billets of iron weighing tons when in direct contact, they will not exert sufficient magnetic force to lift any iron at a distance of only a few inches.Bombs.—The throwing of bombs in the water to intercept the oncoming torpedo might possibly divert its course if the torpedo were seen, but of all the ships that have been lost how few have seen the torpedo which did the damage! The white wake due to the air exhausted from the engines of the torpedo is frequently seen, but the air wake does not show on the surface from a torpedo running at any considerable depth until after the torpedo itself has passed on, as it takes quite some time for the air bubbles to reach the surface, and in a choppy sea the wake is very difficult to see in any case.Discs.—Whirling discs spinning through the water to catch the nose of the torpedo and whirl it out of its course is one of the fanciful schemes which has attracted some press notice. The horsepower required to whirl the discs during one voyage would probably tax the full capacity of the ship to provide fuel and power enough to keep them whirling.C-1, ONE OF THE LATER TYPE FRENCH SUBMARINESFrench-Official Courtesy of Sea Power & Pictorial PressUnsinkable Ships.—Unsinkable ships are possibly practical to a limited extent. Numerous proposals of ship construction along this line have been made, mostly of ships built up on the cellular system. Some proposals have also been made for carrying the cargo in hermetically sealed tanks that would assist in floating the ship if she were torpedoed. The objections to the construction of vessels of this class are its enormously increased cost over the ordinary cargo ship, the reduced carrying capacity per ton of displacement of such vessels, and the impossibility of preventing injury to ships of this sort to such an extent as to make them unmanageable. Any surface ship, to meet fully the submarine menace, must be not onlyunsinkable, but it must also beindestructible. When a ship once becomes unmanageable and incapable of getting away, a powerful mine or mines may be placed at considerable depth under her bottom and the whole fabric blown up into the air.CARGO-CARRYING SUBMARINES OF THE AUTHOR'S DESIGNThey will carry 7500 tons of cargo on a surface displacement of 11,500 tons; their submerged displacement is about 13,500 tons.Convoys.—Convoying a merchant fleet offers perhaps some safety to the individuals on the ships in case some of them are lost, but I cannot see that it offers much protection to the fleet as a whole, as the speed of the fleet is limited to that of the slowest ship, and the smoke or appearance of the leading ships are more apt to give a waiting slow-speed submarine time to catch up with the tail end of the fleet. If it came to a gun fight the fleet might have the advantage, but in experimental work I have frequently run in amidst a fleet of ships, and their first knowledge of my presence was when the periscope was extended above the surface. As it is only necessary to extend this for a period of a few seconds' duration to get the range and bearing of one of the ships to aim the torpedo, the chance of a gunner getting the range and hitting the periscope is very slight, and, even if the periscope were destroyed, it is easy to replace it with a spare one.Smoke Screens.—To hide vessels in clouds of smoke so as to avoid being seen by submarines has been proposed as a method for eluding the U-boats. This procedure would really assist submarine commanders in their search for prey, for the smoke would notify them of the presence of vessels far below the horizon, whose location and course they would otherwise not be aware of. They have a term in the British navy called "firing into the Brown," which means firing at a group of vessels, expecting that a certain percentageof hits will be made, depending on how close a formation of ships is being kept; firing into the "smoke" would be apt to get some. Smoke screens can be used effectively only when the wind happens to be proportionate to the speed of the ships and blowing in the right direction. With a head wind or a strong side wind some of the vessels forming the convoy are sure to be exposed to attack.Zigzag.—Steering zigzag courses adds to the time of crossing from one port to another, and affords only a slight measure of additional safety, as a ship running a zigzag course takes much longer to make a crossing, and is therefore longer exposed to danger; besides, this process adds very materially to the cost of the voyage. It probably does add somewhat to her chances of escape, as a submarine lying in wait anticipating that she will pass within torpedo range might be fooled by her zigzagging out of the way. On the other hand, a submarine might be lying in wait too far to one side of her course to be able to intercept her, and the ship might just as likely as not, not knowing she was there, zigzag right toward her and get caught.In facing the submarine problem, the nations at war with Germany are thus forced to adopt tactics of three kinds: First, to destroy the enemy submarines—I have been informed from reliable sources that England has over five thousand vessels searching for U-boats; second, to make cargo vessels invulnerable to torpedo attacks; and, thirdly, to elude and escape the U-boats. No great measure of success, no great results, have come out of attempts of the first two orders; the U-boats have in general gone unscathed, and they have inflicted damage of such an appalling nature as to terrify those cognizant of the shipping needs of Europe.In my judgment, however, efforts to combat the submarine should be concentrated on devising ways and means to elude it; this is the only solution which promises results. I shall therefore devote the remainder of this chapter to a discussion of the problem of eluding submarines and how it may best be accomplished.Cargo Submarines.—In my judgment, the only way that any nation will be able ultimately to continue its commerce with any degree of safety or certainty when blockaded by submarines will be by the construction of large merchant submarines which will be able to evade the enemy U-boats successfully.I have pointed out above that "submarines cannot fight submarines," because they cannot see or locate each other. It is this very thing which will enable the cargo-carrying submarine to evade the military submarine. They are also able to evade all surface craft, either friend or foe. Captain Paul Koenig, of theDeutschland, told me that most of his journey in theDeutschlandwas upon the surface. He stated that her low visibility enabled him to see all approaching ships before they could see her, and that it was only necessary for him to submerge and rest until the surface ship had passed on her way. The tactics of the larger cargo-carrying submarines would be the same. They need not have much radius of action when submerged; all they need to do is to hide until the danger has passed. If desired, however, their radius of submerged action may be increased to equal or largely exceed that of a military submarine, but this would unnecessarily increase their cost of construction; otherwise the cost of building such vessels should not exceed twenty-five per cent. more than the cost of constructing a first-class surface ship.Now I have prepared a few diagrams showing the advantage of various types of vessels in evading the submarine, and of these I shall treat immediately, as they illustrate the points of my contention perfectly. There was a time when everybody thought the earth was flat, but now I believe it is generally conceded that it is round. Every one knows that when the sun or moon sinks beneath the horizon it cannot be seen, neither can anything else which is below the horizon, so if the horizon intervenes between two distant observers they cannot see each other. Now by referring to our text-books we find that if an observer is stationed at a height of fifteen feet above the surface of the sea the horizon is five and one-eighths miles distant, so that if there were another observer stationed on the other side of the horizon at the same distance and height from the surface of the sea they could not see each other, as the surface of the earth or sea, being round, would stand up like a hill between them.THE "DEUTSCHLAND"By Courtesy of MotorshipThe "Deutschland" was the first submarine cargo-carrier to cross the Atlantic Ocean. She was under the command of Captain Paul Koenig and proved the practicability of running the English blockade four times before war between Germany and the United States caused her owners to discontinue her sailings. Had war not come between the two countries, her German owners would undoubtedly have had submarine cargo-carrying vessels making weekly sailings between the United States and Germany.The diagram shown herewith shows the distance of horizon in miles from 0 to two hundred feet elevation above the surface of the water.I have drawn a sketch—in which the scale of distance is exaggerated in order to better illustrate my meaning—of the earth's surface to show the comparative visibility of vessels when seen from a military submarine, lying in wait, with periscope extended fifteen feet above water. Now take such ships as theLusitania, shown in position No. 5 on the diagram, with her smoke-stacks extending over one hundred feet above the surface of the sea; their tops would appear above the horizon and become visible to a distant observer with a powerful glass, stationed at, say, fifteen feet above the surface, at a distance of about eighteen and three-eighthsmiles. Her smoke-stack would also become visible through a telescopic periscope, the object glass of which was extended fifteen feet above the surface, while men seated in a rowboat could not see each other because of the intervening "hill," so to speak, at a distance of four miles apart. If they were under water in a submarine they could not see each other at all unless they had the periscopes elevated above the surface. In that case it would not be possible for one periscope to see another at any considerable distance, because the periscope is such a small object, and vision through it does not compare with natural vision, owing to the fact that there is considerable loss of light in passing the image of external objects through lenses and prisms. Hence it has been found necessary to reduce the field of vision to about one-half that of natural vision to give the effect of true distance, and as soon as twilight falls it is practically useless. I have taken fifteen feet above the surface without the submarine's conning tower showing, for if her conning tower is shown above the surface she is in danger of being herself discovered.From the above data we are able to determine the probability of being discovered. We take the case of the largest and fastest ocean liners, such as theLusitaniaas one illustration. We will assume that theLusitaniais making her maximum speed of about twenty-five knots, which is about the maximum of speed yet attained in a large surface freight-and passenger-carrying ship, and from our scale of vision as applied to upper diagram No. 5 we see that her top works will become visible above the horizon at a distance of eighteen and three-eighths miles from the periscope of the submarine. The commander in the submarine, by using his range anddirection finder with which all military submarines are fitted, finds the ship to be pursuing a course and speed that will cause her to pass probably within ten miles of the submarine station in about thirty-five minutes, which is too far off to attack by torpedo. Now, while submarines have a submerged speed of only about ten knots, the commander is quickly able to ascertain that he can intercept the twenty-five-knot boat by laying his own course at right angles to the approaching ship, and that, if the ship keeps her course and speed, in thirty-five minutes he can be within torpedo range, as will be seen by reference to this sketch (see diagram, position No. 5).DIAGRAM TO ILLUSTRATE THE COMPARATIVE VISIBILITY AND CONSEQUENTLY THE COMPARATIVE SAFETY OF SURFACE SHIPS AND CARGO-CARRYING SUBMARINESNow take for another comparison a slow-speed merchantman of the tramp type making ten knots, which is about the economical speed for this class of ship. Her smoke might be the first thing to betray her approach, but for purposes of comparison take her smoke-stack also, which is the first solid portion of the ship to appear. The smoke-stacks of this class of vessel would probably not be over forty feet in height above water level, therefore, if she were making the same course as the high-speed ship, it will be observed by referring to diagram, position No. 4, and the distance and speeds mentioned thereon, that the submarine at a speed of ten knots has more time to get nearer the course of the approaching ship and can have more time to calculate the enemy's speed of approach and direct course, and thus launch his torpedo with more certainty of making a hit. But assume that this approaching slow-speed ship had no solid opaque portion extending over fifteen feet above the surface of the water, as is the case in a cargo submarine as shown in position No. 3 on the diagram of the earth's surface. One now seesthat she would pass the waiting submarine below the horizon, and the intervening round of the sea's surface would prevent the submarine from seeing her; thus she would pass by unseen and in safety.The above series of diagrams will show the percentage of safety of ships of different characteristics when coming within the range of visibility of a submarine lying on the ocean highway waiting for passing ships; the submarine is assumed to have a submerged speed of ten knots in each instance. From an analysis of these diagrams it cannot be denied that practically one hundred per cent. safety could be secured could these cargo-carrying submarines cross the ocean from one friendly port to another and remain invisible during the entire journey, but at the present time this is impossible, because there is no known means of supplying sufficient power for long under-water voyages without drawing on the upper air in large quantities to assist combustion in either prime or secondary power-generating machinery.The diagram plainly shows that a cargo-carrying submarine running awash, with her periscope and air intakes only above the water line, may approach within about five and three-quarters miles of any waiting military submarine without danger of being seen, as her "wake" would be below the horizon. Such cargo-carrying submarines can be built and can cross the Atlantic Ocean in this condition at a speed of about ten knots, and by maintaining a sharp lookout would have as much chance of seeing a military submarine as the military submarine would have of seeing them; and by the application of certain tried devices which I do not feel it proper to disclose at this time, but which are within the knowledge of our government authorities, the range of visibilitycan, I believe, be reduced to less than one mile. This type of vessel can almost instantly become entirely invisible by submerging at the least intimation of danger.Such a type of vessel travelling with a freeboard of five feet would become visible to a submarine lying in ambush when she approached within eight miles. This increases the area of danger from one hundred and three square miles, as shown in diagram, position No. 1, in the first instance to two hundred and one square miles, as per diagram corresponding to position No. 2, but in comparison with the usual type of surface cargo-carrying ship of the so-called tramp type she is comparatively safe, as she has the ability to submerge in less than two minutes; and it is hardly likely that she would be attacked without warning, for fear she might be a friendly military submarine. Any communication in the way of wireless, sound, or other signals would, if she were a merchant ship, give her warning, and she would at once submerge, as her only business would be to deliver her cargo and not communicate with or expose herself toeither friend or foe. When far from land she might take a chance and navigate entirely on the surface with a freeboard of fifteen feet, in which condition she can make a speed of eleven knots, as her position No. 3, on the surface of the ocean. This increases the danger area to about three hundred and thirty square miles, as on diagram, position No. 3, about three times the danger area shown on position No. 1, but as the area to be covered by the military submarine on the high seas, far from land, is also much greater, the real danger would be proportionately less than that with the lower visibility in a more thickly infested zone.TORPEDO BEING FIRED FROM THE DECK TUBES OF THE SUBMARINE "SEAL"This vessel was fitted with two double-barrel torpedo guns, housed in a superimposed superstructure. These four torpedoes could be fired to either broadside. The above photograph shows a torpedo in the act of leaving one of these tubes above water. They may be discharged either above or below the surface.High Speed.—Speed is better than no defence, but no one would consider building twenty-five-knot freighters. The cost would be far out of proportion to the service. So long as U-boats do not betray their presence, a fast vessel is almost as liable as a slower one of less freeboard or lower top hamper. One can never tell where the submarine may be lurking, and her capacity to harm is determined by her ability to locate her prey. There are three means available to her to locate her target: first, her own sight; second, her sound-detecting devices; third, by wireless directions given to her by others who may advise her of the vessel's position. Her own sight is the best and usual means for locating her target. The above diagrams show that the largest and fastest ships can be located at much greater distances than the low visibility ships, and that the area of visibility becomes the area of danger, which is practically ten times greater in an expensive, large, high-speed liner over that of the comparatively low-cost cargo-carrying submarine.BRITISH SUBMARINE NO. 3 PASSING NELSON'S OLD FLAGSHIP "VICTORY"This submarine is of the Holland type, similar to the U. S. "Adder" and "Moccasin." This illustration shows the radical change made in naval warfare in one hundred years.One should not imagine that the Germans are carrying on this campaign at random. It is well organized and systematic. Each vessel that comes in sight of a submarine is a marked vessel, and even if she is the fastest vessel afloat, she may speed unwittingly into a trap set for her by wireless. So long as she cannot disappear she has no real ability to elude. On the other hand, the cargo-carrying submarine of low speed has both these advantages: she has low visibility and the capability of disappearance. She may become invulnerable when danger threatens. She has all of the qualities possessed by her enemies. She may beat them at their own game. Vessels of the ordinary type will suffice in no way to meet the great problem presented by the U-boats. The cargosubmarine, however, readily meets all the needs of the situation. This is the sole method of which I am cognizant by means of which a submarine blockade and the destruction of cargo-carrying vessels can be overcome with safety and with certainty. I have expected the Germans would blockade our own ports, as it is easily possible for them to do so; I believe the reason they have not done so thus far is because of political reasons, as it would undoubtedly be to their advantage to have our trade after the war, which they might not have if they arouse our hatred any more than they already have.
In the present European war, for the first time in the world's history, the submarine, as is also the case with the airplane, has taken an important active part, and has become a weapon of unlimited value. We have seen that even as early as the war of the American Revolution the submarine was utilized, but up to modern days the submarine had never been a really significant or consequential factor in naval warfare; its use had been previously but sporadic and experimental. In the wars of the past it had no bearing upon the destinies of nations or the outcome of naval battles. To-day the situation is very different: the submarine has been called into action as a weapon of primary value and is producing tremendous results.
In the conflict in which we are now engaged the destructive capabilities of the submarine have been made use of, for the most part, in the work of commerce destruction and in the task of hampering communication by sea. It has not taken a great deal of active part in actual naval battles, although on some occasions its presence has been severely felt by the fleets of its enemies. But the submarine has been an important factor in naval warfare by reason of the fact that its very presence and the possibility of its use have checked the actions of belligerent fleets of battleships in no inconsiderable way. In writing of this I am reminded of the fact that a short time ago I was introduced to a pleasant-faced,motherly old lady who, when she learned that I was an inventor of submarine boats, exclaimed, "Why! I should not think you could sleep nights from thinking of all those poor people who have been drowned by the U-boats!"
I asked the old lady if she had ever considered the submarine from another angle of view—viz., as a life and property saver in the present war—and she said, "No; how could that be possible?" I then explained to her that had it not been for the existence of the submarines many more lives would have been sacrificed than have been lost by the use of submarines. I asked her to consider what would have been the loss of life if the battleships, cruisers, gunboats, destroyers, etc., had met on the high seas and fought as they were intended to fight. A submarine carries a crew of but a few men, while a battleship may carry a thousand, consequently thousands of men would have been killed in the old-time methods of fighting, compared with the few that have been killed in the submarine warfare. Then again, had it not been for the submarines lying off Russia's, Germany's, England's, France's, Italy's, Austria's, and even Turkey's shores, many seacoast cities, towns, and hamlets would undoubtedly have been bombarded and destroyed, and countless thousands of lives and enormous property valuations lost forever to the world; for one must remember that a life, or a property once erected by hands that are gone, if lost, can never be economically replaced. The only reason such bombardments have not occurred is the fleet commander's fear of that waiting, watching invisible sentinel, the submarine, which lies off the respective combatants' shores; and thus because of its existence thousands of lives and great property valuations have been saved. Thus, while thesubmarine has not been much of a fighter in naval battles, it has, in my opinion, been of great power as a preventer of fighting, and that, after all, is rather more in its favor than against it.
It is, however, the submarine in the role of commerce destroyer which is attracting attention at the present time. The democratic nations of the world are face to face with the problem of transporting men, food, ammunition, and supplies to Europe. The submarine threatens to cut off communication between Europe and the other continents. It is very necessary that means be taken to offset the activities of the submarine. It is this problem which leads me to write upon this topic.
BRITISH SUBMARINE C-2 ARRIVING AT PORTSMOUTH IN A GALENote hydroplanes at centre of conning tower; in later types these were placed under the water, as they were found ineffective in this position
BRITISH SUBMARINE C-2 ARRIVING AT PORTSMOUTH IN A GALENote hydroplanes at centre of conning tower; in later types these were placed under the water, as they were found ineffective in this position
Note hydroplanes at centre of conning tower; in later types these were placed under the water, as they were found ineffective in this position
The devices which have been proposed for capturing and destroying the U-boats in order that navigation upon the Atlantic Ocean may be made safe have run into the thousands. I have had hundreds of impractical schemes sent to me, and the Navy Department and the Naval Consulting Board have been almost swamped by the various suggestions that have been pouring in from all over the country in response to editorials in the newspapers to "Save us from the U-boat!"; "American inventors, rise in your might and strike down this peril which works unseen, like an assassin in the dark!" etc. The devices proposed run all the way from blowing up the whole restricted area or war zone of the ocean to fishing for submarines from aeroplanes, which latter method offers a good chance for sport, at least; and if the submarine designers and commanders were asleep the fishermen might have a good chance of making a catch. Many of my engineering friends with whom I have discussed the U-boat problem have urged upon me that I ought, inorder to save the time, energy, and money of many earnest and patriotic—but misinformed—citizens, to publish some material showing the fallacies in many of these schemes which apparently are so promising, and at the same time to point out wherein some have value, and along what lines I believe success to be attainable.
At the beginning of the war I myself sent to the Navy Department a number of devices for detecting the presence of and destroying submarines in shoal waters, some of which may have already been known to the Navy Department, and several of which I have since seen published as being the ideas of others; this goes to show that where many minds are working toward the solution of any particular problem several are likely to arrive at the same point. In the interest of public policy I do not think that any device hitherto unknown which offers a chance of success if used against an enemy U-boat should be described, and therefore I should not describe any such device if such were known, but shall limit my remarks to a discussion of some of the devices that have been proposed and described publicly. Trying to serve the country by developing a certain idea, when that idea is itself old or impractical, is evidently a waste of mental energy and money. Further, to show how some of these methods of attack may be offset by the submarine commanders will also serve to prevent the country from relying on false defences; the submarine is a real menace, and should not be lightly regarded. I hope to impress upon people that this is a very serious proposition. It is a problem which should and does attract the leading minds of the mechanical world; and it is not to be coped with by any fanciful notions. While the devices proposed thus farare individually very numerous, they may be classified into a few distinct categories. I would designate them as follows:
Offensive Devices:
Defensive Devices:
In considering the practicability or value of these devices, we must first consider the capabilities of the submarine and the proper tactics for her commander to pursue. In a paper read before the Institution of Naval Architects in London, in 1905, I described, illustrated by diagrams, the proper method to be pursued in attacking a surface ship, in which I contended that the commander of a submarine, on sighting an enemy, should always keep the hull of his own boat below the horizon in its relation to the enemy vessel, and try to intercept the approaching vessel by taking frequent observations of her course and speed. When the two vessels approach sufficiently near to make it possible for the larger surface vessel to observe the smaller submarine (the comparative range of visibility being proportionate to the exposed surfaces of the two vessels above the horizon), the submarine should then entirely submerge, with her telescopic periscope withdrawn below the surface of the water to avoid the making of a "wake"—which looks like a white streak on the water. When the commander wishes to make an observation he should first bring his submarine to restand then extend the periscope above the surface for a brief instant only, and thus avoid the chance of being seen. Earlier in the war it was common to detect the submarine by her wake, but now, since the fitting of merchantmen with guns, the above tactics are usually pursued, and the first intimation the crew has of the presence of the submarine is the shock of the explosion caused by the torpedo "striking home."
GERMANY'S U-9 AND SOME OF HER SISTER SUBMARINES
GERMANY'S U-9 AND SOME OF HER SISTER SUBMARINES
AEROPLANE AND SUBMARINE(Drawing by T. E. Lake.)For defense of coast lines aeroplanes and submarines may work in conjunction. Aeroplanes, with their enormous range and high speed can locate surface ships many miles away, beyond the range of a submarine's periscope or sound-detecting devices. It could then direct the submarine by wireless or direct communication. Aeroplanes, however, are of great danger to enemy submarines. Flying at certain altitudes they can see submarines a short distance below the water and swoop down on them, dropping depth bombs or trailing torpedoes.
AEROPLANE AND SUBMARINE(Drawing by T. E. Lake.)For defense of coast lines aeroplanes and submarines may work in conjunction. Aeroplanes, with their enormous range and high speed can locate surface ships many miles away, beyond the range of a submarine's periscope or sound-detecting devices. It could then direct the submarine by wireless or direct communication. Aeroplanes, however, are of great danger to enemy submarines. Flying at certain altitudes they can see submarines a short distance below the water and swoop down on them, dropping depth bombs or trailing torpedoes.
For defense of coast lines aeroplanes and submarines may work in conjunction. Aeroplanes, with their enormous range and high speed can locate surface ships many miles away, beyond the range of a submarine's periscope or sound-detecting devices. It could then direct the submarine by wireless or direct communication. Aeroplanes, however, are of great danger to enemy submarines. Flying at certain altitudes they can see submarines a short distance below the water and swoop down on them, dropping depth bombs or trailing torpedoes.
Aeroplanes and Dirigibles.—These are undoubtedly valuable near land in shallow water,providingthe water is clear and has a bottom in striking contrast to the hull of the submarine. I should consider the dirigible likely to prove of more value than the aeroplane, owing to its ability to hover directly over and regulate its speed to that of the submarine and thus enable itself to drop depth bombs more accurately. Experience has shown that it is almost impossible to calculate where a bomb will strike when dropped from a swiftly moving aeroplane. The chance of its striking the submarine would be very slight. The use of aeroplanes has, however, forced the submarines away from shoal clear water and probably has been instrumental, also, in causing them to become equipped with high-angle rapid-firing guns. In a battle between swiftly moving aeroplanes and submarines with high-powered guns firing shrapnel, the chances are nearly all in favor of the submarine, as they can carry the most powerful guns and are firing from a much more stable platform; in fact, the best analogy I can think of is that of a gunner in a "blind" firing at a flock of ducks passing overhead. Aeroplanes have been used, however, as scouts, merely to detect a submarine and direct surface ships to the attack; also, aeroplanes have directed trawlers to a submarinelying submerged at a shallow depth. This method of attack has undoubtedly been successful in some instances, but where success might have been met with in this manner with the earlier submarine boats, which were not provided with guns, it is now a problem easily met by submarine architects. Submarine boats may be built which have no fear of this combination. One of my earliest designs provided for a revolving armored turret to carry heavy-calibre guns; this revolvable armored turret would extend only above the surface and would carry guns of sufficient calibre to sink any trawler, destroyer, or other craft except an armored ship. It has recently been reported that the Germans are bringing out ships fitted with turrets of this type, and as they are familiar with my designs from the Patent Office specifications, and also have my working drawings of a large cruiser submarine mounted with guns, in 1905, I have no doubt that the report is true, as they have consistently been the first to adopt such new devices as may be needed to offset any attack against their submarines, or to increase their means of offence against surface craft without relying upon torpedoes alone. As far back as 1902 theProtectorwas fitted with a small gun on top of her conning tower, with the breech extended into the sighting hood and a tampon controlled from within the turret for closing the muzzle, so that no water would enter the barrel when the vessel was submerged, thus permitting a new cartridge and shell to be inserted into the breech when submerged; then, by momentarily bringing the conning tower above the surface, we could fire, then submerge and reload, rest and fire again, etc., thus providing a disappearing gun on a very stable platform.
In deep water the submarine may readily escape detection by aeroplanes by sinking below the depth to which vision can penetrate. This depends upon the amount of foreign substance held in suspension in the water. Along the Atlantic coast it is possible to see only a few feet; as you go off shore vision becomes clearer, and it would probably vary during the dry seasons from four to five feet near shore to forty or fifty feet well off shore. The greatest distance I was ever able to see in my experiments in the Chesapeake Bay with a powerful searchlight was forty feet. In Long Island Sound one can seldom see over fifteen feet, and after storms, when sediment is carried into the Sound, sometimes it is difficult to see over three or four feet. I have been down on muddy bottom at a depth of one hundred feet and could not see my hand held close to my face. At a depth of one hundred and twenty-five feet in the Baltic on sandy bottom I was able to see twenty-five feet. This was about eight miles off shore, opposite Libau, Russia. In the English Channel the frequent storms stir up so much sediment that it is seldom possible to see over fifteen feet, while in the Mediterranean and our Southern waters near the Florida coast, near Nassau, and in the Caribbean Sea, it is possible at times to see seventy-five or even one hundred feet. Now there are means available to the submarine to enable it to lie at rest submerged at depths exceeding one hundred feet, and yet have a full view of surface ships and also to scan the heavens, therefore I would say that aeroplanes and dirigibles will prove ineffective against submarines fitted with revolvable turrets, high-angle firing guns, or where they may be operating in clear water exceeding one hundred feet in depth or in shallow water where the sediment held insuspension is in sufficient quantity to prevent discovery. Aviators with whom I have discussed this problem tell me they can seldom detect objects lying on the bottom, even in comparatively shallow water.
RUSSIAN CRUISER-LAKE TYPE SUBMARINE IN SHED BUILT BY PETER THE GREAT—1905This was the first large submarine of the cruiser type, built substantially after the design submitted by the author to the U. S. Navy in 1901.
RUSSIAN CRUISER-LAKE TYPE SUBMARINE IN SHED BUILT BY PETER THE GREAT—1905This was the first large submarine of the cruiser type, built substantially after the design submitted by the author to the U. S. Navy in 1901.
This was the first large submarine of the cruiser type, built substantially after the design submitted by the author to the U. S. Navy in 1901.
Sound Detectors.—We have heard many claims put forth concerning the great results which were to be attained in fighting the U-boat by the use of various sound-receiving devices in the nature of microphones, in detecting the presence of submarines by hearing the hum of the motors and the noise of their machinery. These devices are proposed both for offensive and defensive purposes. A vessel equipped with such mechanism is believed to be able to escape upon hearing a U-boat, or to seek out the submarine and destroy it. Those who have been expecting so much from this source are probably not aware of the fact that submarine inventors themselves were the first to utilize this method of sound detection under water to enable them to apprehend the presence of other vessels in their vicinity before coming to the surface; they have made use of such devices for years.
I well remember my first long submergence of ten hours' duration down at Hampton Roads, near the mouth of the Chesapeake Bay, July 28, 1898. During this period of submergence the machinery was shut down for a time, and one of the first sensations we experienced was the strange sounds which came to us of the propellers and paddle-wheels of surface vessels passing in our vicinity. The first vessel that we heard was a tugboat; we could tell that by the sound of her puffing exhaust and the characteristic sound of her machinery. We thought at first she was coming right over where we were submerged, and feared she might carry away our masts, which extended above the surface, but she passedon, and then we heard coming at a distance the uneven and characteristic sound of a paddle-wheel steamer as her paddles slapped the surface of the water. Then we heard the slow, heavy pound of an ocean liner coming in, and knew that she had a loose crank-pin or cross-head bearing by the pound every time the crank-pin passed over the dead centre of its shaft. The click, click of the little high-speed launch was also easily detected—all this without any sound receiver on the vessel. Any of us simply sitting or standing anywhere in the submarine could hear outside sounds. By putting the head of an iron bolt against the skin of the ship and sticking the end of the bolt in my ear the sound was much intensified, as the whole steel fabric of the ship became a great sound collector. This led me to make experiments toward determining the direction of the sounds under water, and I applied for a patent on a device which could be swung in different directions, on the theory that the sound waves would be stronger when coming straight from their source, but shortly after this the experiments of Professor Gray and Messrs. Munday and Millett were published and I dropped my application and did nothing further in the matter, as they seemed to have solved the question in a satisfactory manner. Afterward Professor Fessenden brought out his oscillator and improved sound detector, with which it is possible for submarines to carry on wireless conversations under water when at a distance of several hundred feet apart, and to pick up the characteristic sounds of different types of surface ships at considerable distances. Sound detectors are of greater benefit to submarines lying in wait for their enemies than they are to surface vessels, as they enable the submarine to lie at rest, submerged and invisible, herself giving no betrayingsound, while no surface ship can come within the zone of her receiving apparatus without betraying its presence.
Submerged Sound Detectors.—It has been stated that sound detectors connected to shore stations have been able to detect submarines when passing in their vicinity, and, by the triangulation method as applied to the intensity of sounds, observers have been able to tell approximately the location of the U-boat from the sound of the U-boat's machinery. The obvious thing for submarine designers and commanders to do to offset this danger to the submarine is to use noiseless machinery in the U-boats, or to send other U-boats with a wire-cutting grapnel to cut the shore connections of the sound transmitter. It is apparent that this method of attack is applicable only to points close to shore or in places like the English Channel.
A GROUP OF GERMAN U-BOATSNote their broad decks, due to buoyant superstructure.
A GROUP OF GERMAN U-BOATSNote their broad decks, due to buoyant superstructure.
Note their broad decks, due to buoyant superstructure.
RUSSIAN-LAKE TYPE CRUISING SUBMARINE "KAIMAN" MAKING A SURFACE RUN IN ROUGH WEATHER IN THE GULF OF FINLAND
RUSSIAN-LAKE TYPE CRUISING SUBMARINE "KAIMAN" MAKING A SURFACE RUN IN ROUGH WEATHER IN THE GULF OF FINLAND
Deck Guns.—The mounting of deck guns on merchantmen for defence against the submarine has proved of slight value. When it was first proposed to mount guns on American merchant ships I wrote the Navy Department on March 11, 1917, in part as follows: "I have tried, in the interest of this country, to impress this fact upon the people (that the submarine, because it is invisible, is invincible), but I find in talking with many intelligent people, that they do not and cannot comprehend the possibilities of the submarine when it is taken seriously and the effort is made to get all there is out of it, without reference to political, financial, or prejudiced interests. Thedestructivenessof the submarine is growing; devices which were effective in detecting and trapping submarines early in the war are now becoming useless. The theory that putting a gun on a merchant ship is going to protect that ship, her crew and passengers, will,I fear, be equal to the signing of the death-warrant of all that are on that ship if we are at war, as the slogan in to-day's headlines (as per copy clipping enclosed)—'Sink any ship you see'—will be met, I fear, by a German slogan of 'Sink every ship you meet, but don't let themsee youdo it.'"
Since that time many ships fully equipped with arms have been sunk by torpedoes and have never seen the submarines which destroyed them. There is no way to attack submarines by gun fire unless they are seen, and commanders of submarines are becoming expert in concealing their presence.
Submarine Guns, Aerial Torpedoes, Searchlights.—For an under-water gun to be effective, there must first be discovered some way to locate the target; this, of course, is almost impossible. Aerial torpedoes or depth bombs might be effective if the submarine were seen, but it is the business of the submarine commander to keep out of sight. Powerful searchlights have very little chance of picking up the periscope or conning tower of a submarine. I remember lying all one night in theArgonaut, during a storm, at the outer edge of the mine fields off Fortress Monroe, at the time the whole country was in dread of an invasion by Cervera's fleet during the Spanish-American War. We were in forbidden territory, having been delayed by the storm in getting into harbor before "Curfew" rang, so to speak. The powerful searchlights of Fortress Monroe were playing all night, but they did not detect our presence, as only our sighting hood was above water, and presented such a small object, and being painted white, it was not distinguished from the "white caps" on top of the sea caused by the storm.
Searchlights under water are useless because of the particles of foreign matter held in suspension which reflect backthe glare of the light. TheArgonautwas fitted with powerful searchlights and reflectors located in her extreme bow, with a pilot-house or lookout just above the three searchlight windows. The greatest distance we were ever able to see was during some night experiments in the Chesapeake Bay during a long dry spell, when the sediment had had an opportunity to settle, and that was only forty feet. The light would penetrate through the water several hundred feet and make a glow on the surface, but vision could not penetrate the water. For instance, it is said that after a storm a glass of Mississippi River water will show fully an inch of sediment. To see through three or four inches of that kind of water, therefore, one must see through an inch of mud. It is well known that no light has yet been found that will enable vision to penetrate through a heavy fog, due to the reflection of light upon the minute crystals of water held in suspension in the air. It appears hopeless, therefore, to expect vision to locate submarines by seeing through the opaque substance held in suspension in all water.
Echo and Magnetic Devices.—Locating submarines by echo has been proposed, but apparently without thought as to what would happen to the vessel giving out the sound in the effort to get an echo back from a submerged submarine, lying in wait with her "ears" waiting to hear some suspicious sound. Also, magnetic devices for the purpose of detecting submarines, if ever found practical, will probably be kept so busy leading their operators to and investigating large steel ships that have already been sunk by submarines that they will probably miss the little submarine, which can easily sink them while they are investigating these other sunken ships.
Channel and Open-sea Nets.—These have been and are being used with some success, but that success has been attained only because at the beginning of the war the submarines had no means for determining the presence of the nets before becoming entangled in their meshes, and when they once became entangled they had no means to cut themselves loose. Devices are now available which enable the commander of a submarine to locate a net before reaching it, and to destroy that net and all its attached mines with but little danger to his own vessel. To what extent these devices are being used is unknown. However, when the submarine is not especially fitted for the detection and destruction of nets and attached mines, they are probably the most efficient type of trap yet provided for capturing and destroying these "submarine devil fish." TheScientific Americanpublished an article by me in 1915 describing a submarine fitted with mine-evading devices and meant to under-run nets, which has been reproduced in the previous chapter.
THE U-65Photograph copyright by Underwood & UnderwoodOne of the large German U-boats fitted with deck guns hailing a Spanish merchantman which they have held up.
THE U-65Photograph copyright by Underwood & UnderwoodOne of the large German U-boats fitted with deck guns hailing a Spanish merchantman which they have held up.
Photograph copyright by Underwood & Underwood
One of the large German U-boats fitted with deck guns hailing a Spanish merchantman which they have held up.
RUSSIAN-LAKE TYPEThese vessels are powerfully armed, fitted with four torpedo tubes firing fore and aft, also Dzrewiecke apparatus for firing torpedoes to either broadside.
RUSSIAN-LAKE TYPEThese vessels are powerfully armed, fitted with four torpedo tubes firing fore and aft, also Dzrewiecke apparatus for firing torpedoes to either broadside.
These vessels are powerfully armed, fitted with four torpedo tubes firing fore and aft, also Dzrewiecke apparatus for firing torpedoes to either broadside.
The above articles having been published previous to our country entering the war, and being thus of public knowledge, it is permissible to republish them as a method which might be used to advantage in preventing the German submarines from coming out from their bases. It is admitted that the allied fleets are overwhelmingly superior to the German fleet, yet they are impotent to attack the German battle fleet or to make reprisals on Germany for the constant depletion of their merchant fleet, because Germany's fleet of battleships, cruisers, and merchantmen will not come out in the open, but lies safe behind nets and mine fields as their inner defence, using her submarines on her outer line ofdefence. As mentioned, Winston Churchill said we must "dig them out like rats out of a hole." That was over three years ago, but not one has been dug out as yet, and, although it would be a very expensive process to do so, it might be possible, by the coöperation of submarines, surface ships, trawlers, and aeroplanes, to move forward gradually and expansively a double or treble line of nets and to defend such a line of nets just outside of the range of the most powerful shore-defence guns. The battleships should be protected by operating between the line of nets to prevent attack upon them by submarines in the rear. Bottom-working submarines would be needed to clear away the mines and nets of the enemy as the mines and nets were moved forward. Constant patrol and repair of the nets would be maintained under the guns of the net-protected fleet, and allied submarines must be on constant attendance in advance of the first line of nets to meet the concerted attack of a portion of the German fleet in "rushing" the line—which must be expected in the attempt to break the same—in order to let out a fleet of their submarines into the open sea to continue their attacks on the allied and neutral commerce of the world. This seems to me the only practical way of stopping up the hole or holes through which the German submarines come out, and to make it effective it would require a double line of nets and patrol fleets extending from Norway to Scotland, and across the English Channel, and across the entrance to the Dardanelles from Brindisi, Italy, to the Albanian coast. Also, battleships which should be unsinkable and provided with longer-range guns than those of the enemy would be required. Perhaps the combined navies of the world as arrayed against the Central Powers could accomplish it, butunless their guns were more powerful and far-reaching than the shore guns, even then they could not land an invading army.
Submarines vs. Submarines.—Submarines to search for and sink other submarines have been proposed in all sorts of forms and advocated in the press under various titles, such as the "Bloodhounds of the Sea" and other fantastic and sensational captions. Submarines cannot fight submarines, because they cannot see each other, and if they are fitted with noiseless machinery they cannot hear each other. Therefore one might put thousands of submarines in the great ocean, and so long as they kept submerged the chance of their ever finding or colliding with one another would probably be not once in a year.
Derelicts have been known to keep afloat on the ocean for years, although constantly searched for as a menace to navigation. Here the searchers have had sight to aid them, and the object of their search has floated on one plane, the surface of the water, while submarines may navigate or remain at rest at various planes up to a depth of about two hundred feet, which is equivalent to multiplying the area of the ocean to be searched several times, and that in darkness, without the aid of sight to assist. It is ridiculous to think that anything can be accomplished except by the merest chance by one submarine searching for another.
Our attention will now turn to consideration of devices of the second class; namely, those which have been offered as a means of defence against the submarine.
Blinding Searchlight; Blinding Apparatus.—Blinding deviceshave been proposed which aim to direct powerful searchlights against the periscope so as to blind the commander.These are schemes based on very false notions. Submarine commanders frequently have to con their ship against the sun's rays, and have colored glasses to enable them to withstand the intensity of the sun's rays, so that it would be impossible to blind them this way. Further, I cannot imagine a more desirable target for a commander to direct his torpedoes against than a bright spot, either on the surface or submerged, as he knows the searchlight is probably on what he wants to hit; it becomes an illuminated bull's-eye for his target. Again, it has been proposed to blind the periscope by putting a film of oil on the surface to obscure the object glass of the periscope when it emerges through this oil, and a member of one of the British commissions told me he knew of shiploads of oil being pumped overboard, possibly for this purpose, or to show the course of a periscope through its "slick." Some periscopes have been built with means for squirting alcohol, gasoline, or other substances to clear the object glass if ice or salt forms on it. A device of this kind would clear off the oil.
Nets; Plates.—There have been many devices proposed for warding off the torpedoes, the usual weapon of the submarine. The most common of these schemes designate the use of nets or plates suspended from booms carried out from the sides of the ship and extending down into the water. Any device of this kind seriously handicaps the ship's speed, and, if she is once sighted by a submarine, is almost sure to be come up with and attacked. Plates, to be effective against a broadside attack, would need to be the full length and extend to the full depth of the ship. Now, skin friction of a ship's plating is the principal resistance to be overcome in forcing a ship through the water up to speeds of aboutten knots, the average speed of the cargo-carrying ship. If you increase the speed beyond ten knots, other resistances come more prominently into effect, such as wave-making resistance, etc. Now a ship afloat has two sides, while a plate suspended in the water equal to the length and depth of the ship also must have two sides, and thus presents nearly the same square feet of plate surface to the friction of the passing waters as the two sides of the ship, and two plates, one on each side, present nearly twice the area and thus very materially reduce the speed. This resistance is further augmented by the roll and pitch of the vessel, and in a severe storm the plates would be unmanageable and of great danger to the ship itself. The resistance of nets with its vertical members is much greater than that of plates. To get some idea of what the resistance of a vertical rod extending down into the water is, take a broom handle and attempt to hold it vertical when it is extended down into the water from a launch running at about ten knots; it is almost impossible to hold it. A net with a mesh fine enough to catch a torpedo would consist of thousands of vertical members as well as horizontal members extending down into the water.
I have been informed by one naval architect of standing who investigated this phase of the problem that nets of sufficient strength to protect the sides of a ten-knot ship from a torpedo attack cut the speed of the ship from ten knots down to two and one-half knots per hour. It would therefore take a ship protected in this way four times as long to make her voyage; her chance of discovery would therefore be four times as great and her chance of destruction, if once discovered, be almost certain, as a submarinecould readily overtake her and plant mines in her course or even tow a mine underneath her bottom and explode it there, which would destroy the ship much more completely and quickly than a Whitehead torpedo exploded against her side. Devices have also been developed which enable a torpedo to dive under a net and explode under a ship's bottom by a slightly delayed detonator.
Torpedoes have also been built with net-cutting devices, and they have been known to penetrate a ship's plating and sink the vessel without exploding. It is not an easy matter to stop a projectile weighing nearly a ton speeding at thirty-five or forty miles an hour. I can see no hope in stopping the submarine menace by any device in this class.
Magnets.—Some proposals have been made to divert the torpedo by powerful magnets extended out beyond the sides of the ship or at the ends—on the theory, I suppose, of fishing for little fish in a pan of water—the Whitehead torpedo being built of steel in this country and England. It is not generally known that the Schwartzkopf torpedo built by the Germans is built of bronze, or at least it was when I went through their works in Berlin several years ago. Even were it of steel, I doubt if a magnet could be built powerful enough to attract or divert a Whitehead steel torpedo from its course unless it passed very close to the magnet, as any artificially erected magnetic force diminishes in strength very rapidly as the distance from the object is increased. Recall, for instance, the powerful magnets used in handling scrap and pig iron; while they will lift pigs or billets of iron weighing tons when in direct contact, they will not exert sufficient magnetic force to lift any iron at a distance of only a few inches.
Bombs.—The throwing of bombs in the water to intercept the oncoming torpedo might possibly divert its course if the torpedo were seen, but of all the ships that have been lost how few have seen the torpedo which did the damage! The white wake due to the air exhausted from the engines of the torpedo is frequently seen, but the air wake does not show on the surface from a torpedo running at any considerable depth until after the torpedo itself has passed on, as it takes quite some time for the air bubbles to reach the surface, and in a choppy sea the wake is very difficult to see in any case.
Discs.—Whirling discs spinning through the water to catch the nose of the torpedo and whirl it out of its course is one of the fanciful schemes which has attracted some press notice. The horsepower required to whirl the discs during one voyage would probably tax the full capacity of the ship to provide fuel and power enough to keep them whirling.
C-1, ONE OF THE LATER TYPE FRENCH SUBMARINESFrench-Official Courtesy of Sea Power & Pictorial Press
C-1, ONE OF THE LATER TYPE FRENCH SUBMARINESFrench-Official Courtesy of Sea Power & Pictorial Press
French-Official Courtesy of Sea Power & Pictorial Press
Unsinkable Ships.—Unsinkable ships are possibly practical to a limited extent. Numerous proposals of ship construction along this line have been made, mostly of ships built up on the cellular system. Some proposals have also been made for carrying the cargo in hermetically sealed tanks that would assist in floating the ship if she were torpedoed. The objections to the construction of vessels of this class are its enormously increased cost over the ordinary cargo ship, the reduced carrying capacity per ton of displacement of such vessels, and the impossibility of preventing injury to ships of this sort to such an extent as to make them unmanageable. Any surface ship, to meet fully the submarine menace, must be not onlyunsinkable, but it must also beindestructible. When a ship once becomes unmanageable and incapable of getting away, a powerful mine or mines may be placed at considerable depth under her bottom and the whole fabric blown up into the air.
CARGO-CARRYING SUBMARINES OF THE AUTHOR'S DESIGNThey will carry 7500 tons of cargo on a surface displacement of 11,500 tons; their submerged displacement is about 13,500 tons.
CARGO-CARRYING SUBMARINES OF THE AUTHOR'S DESIGNThey will carry 7500 tons of cargo on a surface displacement of 11,500 tons; their submerged displacement is about 13,500 tons.
They will carry 7500 tons of cargo on a surface displacement of 11,500 tons; their submerged displacement is about 13,500 tons.
Convoys.—Convoying a merchant fleet offers perhaps some safety to the individuals on the ships in case some of them are lost, but I cannot see that it offers much protection to the fleet as a whole, as the speed of the fleet is limited to that of the slowest ship, and the smoke or appearance of the leading ships are more apt to give a waiting slow-speed submarine time to catch up with the tail end of the fleet. If it came to a gun fight the fleet might have the advantage, but in experimental work I have frequently run in amidst a fleet of ships, and their first knowledge of my presence was when the periscope was extended above the surface. As it is only necessary to extend this for a period of a few seconds' duration to get the range and bearing of one of the ships to aim the torpedo, the chance of a gunner getting the range and hitting the periscope is very slight, and, even if the periscope were destroyed, it is easy to replace it with a spare one.
Smoke Screens.—To hide vessels in clouds of smoke so as to avoid being seen by submarines has been proposed as a method for eluding the U-boats. This procedure would really assist submarine commanders in their search for prey, for the smoke would notify them of the presence of vessels far below the horizon, whose location and course they would otherwise not be aware of. They have a term in the British navy called "firing into the Brown," which means firing at a group of vessels, expecting that a certain percentageof hits will be made, depending on how close a formation of ships is being kept; firing into the "smoke" would be apt to get some. Smoke screens can be used effectively only when the wind happens to be proportionate to the speed of the ships and blowing in the right direction. With a head wind or a strong side wind some of the vessels forming the convoy are sure to be exposed to attack.
Zigzag.—Steering zigzag courses adds to the time of crossing from one port to another, and affords only a slight measure of additional safety, as a ship running a zigzag course takes much longer to make a crossing, and is therefore longer exposed to danger; besides, this process adds very materially to the cost of the voyage. It probably does add somewhat to her chances of escape, as a submarine lying in wait anticipating that she will pass within torpedo range might be fooled by her zigzagging out of the way. On the other hand, a submarine might be lying in wait too far to one side of her course to be able to intercept her, and the ship might just as likely as not, not knowing she was there, zigzag right toward her and get caught.
In facing the submarine problem, the nations at war with Germany are thus forced to adopt tactics of three kinds: First, to destroy the enemy submarines—I have been informed from reliable sources that England has over five thousand vessels searching for U-boats; second, to make cargo vessels invulnerable to torpedo attacks; and, thirdly, to elude and escape the U-boats. No great measure of success, no great results, have come out of attempts of the first two orders; the U-boats have in general gone unscathed, and they have inflicted damage of such an appalling nature as to terrify those cognizant of the shipping needs of Europe.In my judgment, however, efforts to combat the submarine should be concentrated on devising ways and means to elude it; this is the only solution which promises results. I shall therefore devote the remainder of this chapter to a discussion of the problem of eluding submarines and how it may best be accomplished.
Cargo Submarines.—In my judgment, the only way that any nation will be able ultimately to continue its commerce with any degree of safety or certainty when blockaded by submarines will be by the construction of large merchant submarines which will be able to evade the enemy U-boats successfully.
I have pointed out above that "submarines cannot fight submarines," because they cannot see or locate each other. It is this very thing which will enable the cargo-carrying submarine to evade the military submarine. They are also able to evade all surface craft, either friend or foe. Captain Paul Koenig, of theDeutschland, told me that most of his journey in theDeutschlandwas upon the surface. He stated that her low visibility enabled him to see all approaching ships before they could see her, and that it was only necessary for him to submerge and rest until the surface ship had passed on her way. The tactics of the larger cargo-carrying submarines would be the same. They need not have much radius of action when submerged; all they need to do is to hide until the danger has passed. If desired, however, their radius of submerged action may be increased to equal or largely exceed that of a military submarine, but this would unnecessarily increase their cost of construction; otherwise the cost of building such vessels should not exceed twenty-five per cent. more than the cost of constructing a first-class surface ship.
Now I have prepared a few diagrams showing the advantage of various types of vessels in evading the submarine, and of these I shall treat immediately, as they illustrate the points of my contention perfectly. There was a time when everybody thought the earth was flat, but now I believe it is generally conceded that it is round. Every one knows that when the sun or moon sinks beneath the horizon it cannot be seen, neither can anything else which is below the horizon, so if the horizon intervenes between two distant observers they cannot see each other. Now by referring to our text-books we find that if an observer is stationed at a height of fifteen feet above the surface of the sea the horizon is five and one-eighths miles distant, so that if there were another observer stationed on the other side of the horizon at the same distance and height from the surface of the sea they could not see each other, as the surface of the earth or sea, being round, would stand up like a hill between them.
THE "DEUTSCHLAND"By Courtesy of MotorshipThe "Deutschland" was the first submarine cargo-carrier to cross the Atlantic Ocean. She was under the command of Captain Paul Koenig and proved the practicability of running the English blockade four times before war between Germany and the United States caused her owners to discontinue her sailings. Had war not come between the two countries, her German owners would undoubtedly have had submarine cargo-carrying vessels making weekly sailings between the United States and Germany.
THE "DEUTSCHLAND"By Courtesy of MotorshipThe "Deutschland" was the first submarine cargo-carrier to cross the Atlantic Ocean. She was under the command of Captain Paul Koenig and proved the practicability of running the English blockade four times before war between Germany and the United States caused her owners to discontinue her sailings. Had war not come between the two countries, her German owners would undoubtedly have had submarine cargo-carrying vessels making weekly sailings between the United States and Germany.
By Courtesy of Motorship
The "Deutschland" was the first submarine cargo-carrier to cross the Atlantic Ocean. She was under the command of Captain Paul Koenig and proved the practicability of running the English blockade four times before war between Germany and the United States caused her owners to discontinue her sailings. Had war not come between the two countries, her German owners would undoubtedly have had submarine cargo-carrying vessels making weekly sailings between the United States and Germany.
The diagram shown herewith shows the distance of horizon in miles from 0 to two hundred feet elevation above the surface of the water.
I have drawn a sketch—in which the scale of distance is exaggerated in order to better illustrate my meaning—of the earth's surface to show the comparative visibility of vessels when seen from a military submarine, lying in wait, with periscope extended fifteen feet above water. Now take such ships as theLusitania, shown in position No. 5 on the diagram, with her smoke-stacks extending over one hundred feet above the surface of the sea; their tops would appear above the horizon and become visible to a distant observer with a powerful glass, stationed at, say, fifteen feet above the surface, at a distance of about eighteen and three-eighthsmiles. Her smoke-stack would also become visible through a telescopic periscope, the object glass of which was extended fifteen feet above the surface, while men seated in a rowboat could not see each other because of the intervening "hill," so to speak, at a distance of four miles apart. If they were under water in a submarine they could not see each other at all unless they had the periscopes elevated above the surface. In that case it would not be possible for one periscope to see another at any considerable distance, because the periscope is such a small object, and vision through it does not compare with natural vision, owing to the fact that there is considerable loss of light in passing the image of external objects through lenses and prisms. Hence it has been found necessary to reduce the field of vision to about one-half that of natural vision to give the effect of true distance, and as soon as twilight falls it is practically useless. I have taken fifteen feet above the surface without the submarine's conning tower showing, for if her conning tower is shown above the surface she is in danger of being herself discovered.
From the above data we are able to determine the probability of being discovered. We take the case of the largest and fastest ocean liners, such as theLusitaniaas one illustration. We will assume that theLusitaniais making her maximum speed of about twenty-five knots, which is about the maximum of speed yet attained in a large surface freight-and passenger-carrying ship, and from our scale of vision as applied to upper diagram No. 5 we see that her top works will become visible above the horizon at a distance of eighteen and three-eighths miles from the periscope of the submarine. The commander in the submarine, by using his range anddirection finder with which all military submarines are fitted, finds the ship to be pursuing a course and speed that will cause her to pass probably within ten miles of the submarine station in about thirty-five minutes, which is too far off to attack by torpedo. Now, while submarines have a submerged speed of only about ten knots, the commander is quickly able to ascertain that he can intercept the twenty-five-knot boat by laying his own course at right angles to the approaching ship, and that, if the ship keeps her course and speed, in thirty-five minutes he can be within torpedo range, as will be seen by reference to this sketch (see diagram, position No. 5).
DIAGRAM TO ILLUSTRATE THE COMPARATIVE VISIBILITY AND CONSEQUENTLY THE COMPARATIVE SAFETY OF SURFACE SHIPS AND CARGO-CARRYING SUBMARINES
DIAGRAM TO ILLUSTRATE THE COMPARATIVE VISIBILITY AND CONSEQUENTLY THE COMPARATIVE SAFETY OF SURFACE SHIPS AND CARGO-CARRYING SUBMARINES
Now take for another comparison a slow-speed merchantman of the tramp type making ten knots, which is about the economical speed for this class of ship. Her smoke might be the first thing to betray her approach, but for purposes of comparison take her smoke-stack also, which is the first solid portion of the ship to appear. The smoke-stacks of this class of vessel would probably not be over forty feet in height above water level, therefore, if she were making the same course as the high-speed ship, it will be observed by referring to diagram, position No. 4, and the distance and speeds mentioned thereon, that the submarine at a speed of ten knots has more time to get nearer the course of the approaching ship and can have more time to calculate the enemy's speed of approach and direct course, and thus launch his torpedo with more certainty of making a hit. But assume that this approaching slow-speed ship had no solid opaque portion extending over fifteen feet above the surface of the water, as is the case in a cargo submarine as shown in position No. 3 on the diagram of the earth's surface. One now seesthat she would pass the waiting submarine below the horizon, and the intervening round of the sea's surface would prevent the submarine from seeing her; thus she would pass by unseen and in safety.
The above series of diagrams will show the percentage of safety of ships of different characteristics when coming within the range of visibility of a submarine lying on the ocean highway waiting for passing ships; the submarine is assumed to have a submerged speed of ten knots in each instance. From an analysis of these diagrams it cannot be denied that practically one hundred per cent. safety could be secured could these cargo-carrying submarines cross the ocean from one friendly port to another and remain invisible during the entire journey, but at the present time this is impossible, because there is no known means of supplying sufficient power for long under-water voyages without drawing on the upper air in large quantities to assist combustion in either prime or secondary power-generating machinery.
The diagram plainly shows that a cargo-carrying submarine running awash, with her periscope and air intakes only above the water line, may approach within about five and three-quarters miles of any waiting military submarine without danger of being seen, as her "wake" would be below the horizon. Such cargo-carrying submarines can be built and can cross the Atlantic Ocean in this condition at a speed of about ten knots, and by maintaining a sharp lookout would have as much chance of seeing a military submarine as the military submarine would have of seeing them; and by the application of certain tried devices which I do not feel it proper to disclose at this time, but which are within the knowledge of our government authorities, the range of visibilitycan, I believe, be reduced to less than one mile. This type of vessel can almost instantly become entirely invisible by submerging at the least intimation of danger.
Such a type of vessel travelling with a freeboard of five feet would become visible to a submarine lying in ambush when she approached within eight miles. This increases the area of danger from one hundred and three square miles, as shown in diagram, position No. 1, in the first instance to two hundred and one square miles, as per diagram corresponding to position No. 2, but in comparison with the usual type of surface cargo-carrying ship of the so-called tramp type she is comparatively safe, as she has the ability to submerge in less than two minutes; and it is hardly likely that she would be attacked without warning, for fear she might be a friendly military submarine. Any communication in the way of wireless, sound, or other signals would, if she were a merchant ship, give her warning, and she would at once submerge, as her only business would be to deliver her cargo and not communicate with or expose herself toeither friend or foe. When far from land she might take a chance and navigate entirely on the surface with a freeboard of fifteen feet, in which condition she can make a speed of eleven knots, as her position No. 3, on the surface of the ocean. This increases the danger area to about three hundred and thirty square miles, as on diagram, position No. 3, about three times the danger area shown on position No. 1, but as the area to be covered by the military submarine on the high seas, far from land, is also much greater, the real danger would be proportionately less than that with the lower visibility in a more thickly infested zone.
TORPEDO BEING FIRED FROM THE DECK TUBES OF THE SUBMARINE "SEAL"This vessel was fitted with two double-barrel torpedo guns, housed in a superimposed superstructure. These four torpedoes could be fired to either broadside. The above photograph shows a torpedo in the act of leaving one of these tubes above water. They may be discharged either above or below the surface.
TORPEDO BEING FIRED FROM THE DECK TUBES OF THE SUBMARINE "SEAL"This vessel was fitted with two double-barrel torpedo guns, housed in a superimposed superstructure. These four torpedoes could be fired to either broadside. The above photograph shows a torpedo in the act of leaving one of these tubes above water. They may be discharged either above or below the surface.
This vessel was fitted with two double-barrel torpedo guns, housed in a superimposed superstructure. These four torpedoes could be fired to either broadside. The above photograph shows a torpedo in the act of leaving one of these tubes above water. They may be discharged either above or below the surface.
High Speed.—Speed is better than no defence, but no one would consider building twenty-five-knot freighters. The cost would be far out of proportion to the service. So long as U-boats do not betray their presence, a fast vessel is almost as liable as a slower one of less freeboard or lower top hamper. One can never tell where the submarine may be lurking, and her capacity to harm is determined by her ability to locate her prey. There are three means available to her to locate her target: first, her own sight; second, her sound-detecting devices; third, by wireless directions given to her by others who may advise her of the vessel's position. Her own sight is the best and usual means for locating her target. The above diagrams show that the largest and fastest ships can be located at much greater distances than the low visibility ships, and that the area of visibility becomes the area of danger, which is practically ten times greater in an expensive, large, high-speed liner over that of the comparatively low-cost cargo-carrying submarine.
BRITISH SUBMARINE NO. 3 PASSING NELSON'S OLD FLAGSHIP "VICTORY"This submarine is of the Holland type, similar to the U. S. "Adder" and "Moccasin." This illustration shows the radical change made in naval warfare in one hundred years.
BRITISH SUBMARINE NO. 3 PASSING NELSON'S OLD FLAGSHIP "VICTORY"This submarine is of the Holland type, similar to the U. S. "Adder" and "Moccasin." This illustration shows the radical change made in naval warfare in one hundred years.
This submarine is of the Holland type, similar to the U. S. "Adder" and "Moccasin." This illustration shows the radical change made in naval warfare in one hundred years.
One should not imagine that the Germans are carrying on this campaign at random. It is well organized and systematic. Each vessel that comes in sight of a submarine is a marked vessel, and even if she is the fastest vessel afloat, she may speed unwittingly into a trap set for her by wireless. So long as she cannot disappear she has no real ability to elude. On the other hand, the cargo-carrying submarine of low speed has both these advantages: she has low visibility and the capability of disappearance. She may become invulnerable when danger threatens. She has all of the qualities possessed by her enemies. She may beat them at their own game. Vessels of the ordinary type will suffice in no way to meet the great problem presented by the U-boats. The cargosubmarine, however, readily meets all the needs of the situation. This is the sole method of which I am cognizant by means of which a submarine blockade and the destruction of cargo-carrying vessels can be overcome with safety and with certainty. I have expected the Germans would blockade our own ports, as it is easily possible for them to do so; I believe the reason they have not done so thus far is because of political reasons, as it would undoubtedly be to their advantage to have our trade after the war, which they might not have if they arouse our hatred any more than they already have.