I. TYPES
Sealing up a vessel in order to submerge it was accomplished many years ago. The early attempts succeeded in producing submarines capable of operating on the surface with small buoyancy, or else sliding along the bottom with negative buoyancy. It was not until the early eighties that a vessel was designed which might be said to have been successful in navigating between the stir face and the bottom.
The history of the development of the modern submarine is closely connected with the development of reliable methods of propulsion for a type of vessel designed to travel both on and under the surface of the sea.
As regards hull construction, two distinct types have been developed; the single-hull type being the original conception. The double-hull type was designed in order to gain high surface speed on a moderate length.
The early submarines of the American-Holland type were single-hull vessels. The hull was in the shape of a spindle, largest diameter in the Middle, narrowing toward the ends t water ballast was admitted into tanks contained within the spindle hull. After the vessel had been submerged with but small buoyancy and was traveling at the surface, a single stern diving rudder was used to cause the vessel to "dive." Once the bow went under, the forward deck acted as a hydroplane, and the vessel dove beneath the surface. Leveling at any desired depth was accomplished by means of this diving rudder. Considerable inclination could be used in submerging the early vessels of this type. As tonnage increased, and in consequence the length of vessels increased, a pair of bow diving rudders were added. These were operated together with the after diving rudder, permitting submergence at a small angle of inclination.. Three degrees is the maximum angle usually reached by vessels of the single-hull type so fitted in ordinary smooth water work.
When it is desired to have high surface speed without unduly increasing the length of the vessel, surface buoyance becomes important. Increased surface buoyancy was accomplished by working a hull outside of the central spindle hull. In certain designs this outer hull was only partial, while in others it was run the entire length of the vessel. A submarine with this double-hull construction is usually termed a submersible.
The submersible is operated in a similar manner to a submarine (single-hull type). In addition to bow and stern diving rudders, hydroplanes are sometimes fitted. This type appears to submerge on a level keel, but actually from two to three degrees of inclination is reached.
The single-hull type may be considered a vessel primarily designed to run below the surface of the sea. The form of hull and the small increased amount of wetted surface over that in the light condition gives efficient submerged qualities. The double-hull vessel or submersible, on the other hand, being designed for high surface speed (increased surface buoyancy and surface underwater lines) is primarily a high-speed surface vessel capable of submerging at will.
TABLE I
COMPARISON OF THE TWO TYPES
| Single Hull | Double Hull |
Length over all | 173’ | 197’ |
Surface displacement (tons) | 485 | 485 |
Net submerged displacement | 593 | 643 |
Gross submerged displacement | 655 | 750 |
Net buoyancy—% of surface displacement | 22 | 33 |
Net buoyancy—% of submerged displacement | 18 | 25 |
Shaft horsepower for 14 knots | 800 | 850 |
Net submerged displacement is exclusive of superstructure, from which it is not possible to expel water when submerged. Gross submerged displacement includes superstructure, etc. Net buoyancy means the difference between the surface displacement and the net submerged displacement, and represents the buoyancy on the surface created by expelling water from the ballast tanks.
In the table is shown an actual comparison between a single-hull vessel and a double-hull vessel of the same surface displacement. The double-hull vessel has so per cent more buoyancy on the surface and therefore will be drier in a seaway. The power required to drive the double-hull at the moderate speed of 14 knots is more than that required to drive the single-hull—the wetted surface of the double-hull is greater. However, if we could obtain the horsepower at 15 knots and above, we would find that the longer vessel, the double-hull type would require less S. H. P. than the single-- hull. If, therefore, it is desired to drive the vessel beyond about I41-15 knots on the surface, then the double-hull type will permit the speed on less horsepower and the vessel will have sufficient surface buoyancy to be dry and weatherly. When a submarine is to have a high surface speed in proportion to its length, greater percentage of buoyancy being required, it happens that the double hull type will give this requirement and the tankage system can be arranged more readily by utilizing the compartments in the outer hull for both fuel and ballast. It has been thought that the dividing line between the two types was a question of tonnage; that is, beyond Goo tons the double hull was necessary; this is not so. It may happen that for certain requirements a double hull may become necessary, for reasons of stability, in a vessel of small tonnage. From a structural standpoint a single-hull vessel of woo tons is simple enough, provided moderate speed only is desired.
As to stability, the double-hull type has comparatively large surface stability, combined with comparatively small submerged stability, while the contrary is the case with the single-hull. The single-hull type must therefore have a more comfortable motion at sea, and where buoyancies are equal it is a better sea boat. The maximum righting moment of the single-hull type submerged is when the vessel is inclined at 90 degrees. in the double-hull type the center of gravity is usually higher than in the case of a single hull of circular or elliptical cross section—when totally, submerged the position of the metacenter is usually low. In all types of submarines, the center of gravity must be below the center of buoyancy when the vessel is submerged.
The United States and England have in the past given preference to the submarine or single-hull type. Both the Holland and Lake designs are of this type. The Lake boats have a large superstructure, part of which is water-tight (not pressure-tight), and use hydroplanes when submerged in addition to diving rudders.
Foreign submarines designed by Laubeuf (France), Laurenti (Italian), and the Germania-Krupp (German) are double-hull vessels. In Europe high surface speed was sought without going to extreme lengths of hull. From the surface standpoint only the most striking advantage of the submersible is the large reserve of buoyancy, giving ample deck space for the crew.
II. MACHINERY
Successful surface propulsion arrived with the development of the internal combustion engine. This engine and the electric storage battery, driving motors, formed an excellent combination of propulsive agencies.
An engine for a submarine represented a difficult problem in internal combustion engine engineering, and this is the reason why so many years elapsed' before a reliable engine was produced. In every case where another type of engine has been used, the reason has been that satisfactory internal combustion engines could not be obtained.
A satisfactory and therefore reliable internal combustion engine is the natural and logical submarine engine.. Using these engines for quick submergence it is only necessary to stop the engines and close the valves in the exhaust piping to prevent flooding the cylinders with salt water; the boat then is ready to submerge in so far as the engines are concerned. Furthermore, but little heat is radiated from the engines themselves. This is a matter of considerable importance to the comfort of the men in the engine-room. Also, as all submarines have motor-driven cooling water pumps, these can be run to further cool off the engines after submerging.
Compared with a steam equipment, which has been considered in order to obtain high surface Speed, there is very little heat radiated from the engine itself, for the reason that cylinders and such parts of the engine which naturally become hot are water-jacketed outside, and the temperature of the jacket water seldom rises to over 100 degrees. In addition, the great amount of air constantly required for the engines keeps the engine-room cool and well ventilated.
The fuels for submarines are gasoline, gas engine oil and fuel oil. In the later submarines, the heavier fuel oil will be used to the exclusion of the lighter gas engine oil. An internal combustion engine, such as the Diesel, for a given power, uses only one-third as much fuel oil as does a steam engine plant. This is a most important point to be considered in deciding upon engines for warships.
The first submarines built for the United States Navy were equipped with gasoline engines; they were of i6o horsepower. The last boats to be built with gasoline engines were the "D" class.
Gasoline, on account of its volatile nature, is not a desirable fuel for a submarine engine, but until 1909-10 no engine builder in this country had attempted to build. a Diesel engine suitable for a submarine boat. The first Diesel engines were installed in our submarines of the "E" and "F" classes. These engines were of the four-cycle non-reversible type, built in this country after foreign designs. Two years later, 1913-14, a demand for a higher surface speed was met by the installation of two-cycle Diesel engines in the "H" class.
In order to appreciate the difficulty in the development of a new type of engine, it should be understood that we allow from 18 months to two years to build a submarine; after commissioning, at least a year must pass before any definite conclusions can be drawn. At all events, actual accomplishment is at least two to three years behind what is considered the best design.
Our submarine engine development actually went ahead of the ability of personnel to run successfully. The experts from the engine builders obtained only occasional good results with the two-cycle engines until after numerous faults had been corrected. These faults, for the most part, could not be foreseen by the designers; it was necessary to discover them one by one in actual running of the engines Under the trying conditions of service.
The consequence of faults in the two-cycle engine has caused a return to the four-cycle.
The use of two engines tandem on each shaft has not been an unqualified success in our navy; due to using the after engines practically all the time, the bearings of those engines in time become lower, and when the forward engines were connected the shafting was found out of line. It has the advantage that one pair of engines can drive the ship to about three-quarters of the full speed. Therefore, in cruising, the after engines can be used and at sufficient load for economy, yet not under severe enough stress to cause undue wear and tear.
If, while running on the after engines at moderate speed, it is desired to go at full speed, the after engines will be brought up to their full speed, and meanwhile the forward engines will be started up without load and then the clutch between the two engines thrown in. By this means no time is lost in stopping to connect engines together.
The storage batteries and motors are ideal for submerged propulsion. They require no air, are noiseless and leave no tell-tale wake behind. In addition, the storage battery supplies power to pumps, steering gear, air compressors and the motors of the ventilating system, besides lighting the vessel throughout. The storage batteries in the first classes of submarine were not as reliable, nor could they be given the intelligent care and attention that batteries to-day in our submarines are receiving. The submarine battery has progressively developed, and to-day gives but little to worry over.
Motor trouble has been one of insulation mostly. The oil saturated atmosphere of a submarine is an efficient searcher after defective insulation.
III. OPERATION
From the standpoint of operation, a submarine must be capable of submerging quickly and expelling its ballast quickly. This is an important consideration in design. In the single-hull type the main ballast tanks, inside the pressure or spindle hull, are divided usually into three tanks, each flooded and blown separately. In the double-hull type, what corresponds to the main ballast tanks are in the outer hull.
The time to flood depends upon the exit opening for water, and the time to expel depends upon the above and also the means employed to expel water. Rotary pumps, motor driven, are used and also low-pressure air compressors, discharging the air into the tanks direct. Pumps or air compressors capable of expelling eight tons of water per minute are said to be installed in modern European submarines.
Before submerging, a submarine of either type must get its longitudinal trim. That is, before admitting water to the main ballast tanks, assurance must be had that the vessel has longitudinal stability; when at rest with ballast tanks full of water, the vessel should be on a level keel. The reason for this may be readily understood when it is realized that as reserve buoyancy diminishes, longitudinal stability falls in an alarming ratio. If with 13 tons of reserve buoyancy we express the longitudinal stability by 100, then:
TABLE II
Reserve buoyancy Longitudinal stability
6 Tons 73
3 1/2 tons 47
800 pounds 7
In the most up-to-date submarines. in Europe, automatic compensating fuel tanks have been installed. Water is forced into the fuel tanks as fuel is used, always keeping fuel tanks full of liquid. The only allowance to be made in getting trim is the difference in weight between water and oil; this can be quickly computed and corrected by means of small trimming tanks. In submarines not fitted with such methods of compensation, trim must be actually obtained by trial before each submerged run, else adjusted while submerged from information from the horizontal steering, a none too safe method. The final act, in totally submerging both types, is accomplished by admitting water into strong pressure tanks located amidships (longitudinal center of gravity) called auxiliary or diving tanks.
Submerged speed and submerged radius of action. The former is dependent upon capacity of battery and motor power, and the latter upon capacity of battery and design of motors. A submarine must submerge immediately upon sighting a ship. If it does not, the ship will discover the submarine and the advantage of surprise will be denied it. A submarine submerged can hardly hope to overtake even the slowest surface vessel unless the latter steers more or less toward the submarine. For this method of attack a high submerged speed for a limited time is desirable. Submerged radius is required to submerge at a long distance from a fleet, and while submerged, doing the greatest amount of damage and then still submerged escape from a chase by surface vessels. In hazy and thick weather, in close proximity to enemy warships, a submarine for successful attack may desire to run submerged for eight or ten hours and still have sufficient battery capacity remaining for a spurt attack.
Surface speed for a submarine is not important in attack at all. On information from scouts it can use high speed to obtain a position ahead of an advancing enemy, but immediately it sights the enemy this high speed cannot be used. A high speed engine, furthermore, is usually one of less reliability than a moderate' speed engine.
Very high surface speed can be obtained by going to great length and a double hull for surface buoyancy. So much space is required for engines and engine auxiliaries that battery space cannot be proportionately increased; the result must be slower speed submerged and less radius submerged than is desirable.
If the engines become inoperative the submarine is useless, for it depends upon its engines to recharge its batteries, and these are the source of all power. This vital fact counsels a reliable submarine engine and should cause designers to hesitate in reducing engine weight per horsepower in order to obtain an elusive knot or more surface speed.
IV. DESIGN
It must be remembered that high surface speed is antagonistic to the submerged qualities of a submarine. High speed in surface vessels is accomplished by great length. A submarine of great length while submerging and when submerged is tender longitudinally (see Table II). In order to keep length moderate, large reserve of buoyancy is supplied. This design will be a quick roller. On account of the large water plane surface the metacenter is some distance above the center of buoyancy, and shifts its position with change of angle of transverse inclination; the result is large metacenter height in surface trim. Another point to be considered is, while going from the light to the submerged condition, the center of buoyancy rises and the center of gravity sinks (unless much ballast is carried in top tanks when center of gravity may change its position but little). Metacentric height therefore diminishes; in some double-hull designs it becomes zero and sometimes even negative.
In recent German submarines the top tanks in the double-hull are much flatter and in some cases are non-water-tight. Even this non-water-tight top tank or superstructure contributes to surface buoyancy, and does not raise the center of gravity upon submerging. It also gives the vessel less metacentric height on the surface and proportionally increases her sea-going qualities in making her steadier in a seaway.
Reserve buoyancy is limited in the single-hull design. For a vessel of about woo tons surface displacement, the limit is reached when about 25 per cent buoyancy of the surface displacement is provided. This means that 250 tons of water ballast is taken for total submergence. Double-hull vessels are given as high as so per cent of reserve buoyancy, and is necessary, of course, if the vessel is to be driven at high speed in rough weather. If the vessel was one of woo tons surface displacement, there would be 500 tons of water ballast to be taken in upon submerging.
The double-hull vessel probably can carry a greater supply of fuel oil, as this is carried in outer tanks. Buoyancy can be temporarily sacrificed if necessary for the purpose. This is likewise possible in the single-hull type, only a greater proportion of buoyancy will thus be sacrificed, which might not be safe.
Characteristics will influence size to such an extent that many have fallen into the habit of considering size a characteristic in itself. The submarine hull designer actually starts his calculations with the amount of net submerged displacement he can have. Then he looks up the surface speed desired, and the length the vessel is to be. From this, reserve buoyancy necessary is worked up and then after subtracting, he has the surface displacement. The higher the buoyancy the smaller the weight the designer has at his disposal to put into the hull, engines, batteries, motors, torpedoes, etc. The characteristics that suffer most with large reserve buoyancy are submerged speed and radius, for the reason that additional displacement and wetted surface must be pushed through the water.
We must first of all determine how we intend to employ our submarines. Until we do that no intelligent decision can be made as to type or tonnage, surface speed or submerged speed, etc. Do we intend concentrating our submarines at a point threatened by an enemy or keeping a certain number at many points along our expansive littoral, giving up the idea of concentration? Shall we use them merely to lie in wait near our coast until an enemy stumbles upon them, or give them the seagoing qualities and radius to travel considerable distances; to seek the enemy? Tactically, shall we consider that submerged speed and radius need not be large, or shall we give our submarines the power to travel far submerged, both in time and distance? After we are decided upon these important points, then we shall be prepared to say what type we need.
Another point in design is worth considering, especially is this true for a submarine. The design may fulfill the requirements of speed, surface and submerged, reserve of buoyance, armament, storage, berthing, stability, operation, etc., and yet the submarine may be so overcrowded with machinery, torpedoes and men as to leave no space for overhaul or work in preparation for battle. The designed hull may fit as tightly as a glove. This is the case in many submarines in service. Furthermore, reliability, a factor depending both upon materiel and personnel, is difficult to write in a specification and is frequently sacrificed to gain higher speed. To insure space and reliability some desire to go so far as to state what shall be the minimum surface tonnage and the minimum weight of machinery per horsepower. It must be realized, however, that by so doing the designer may find himself unnecessarily handicapped without our gaining a material benefit. Careful co-ordination in design and frequent interchange of views between designers and operators may produce the desired result.
V. DEVELOPMENT
The first submarine Diesel engine turned over to the naval personnel to run was in 1912. They were built from German designs. From this date until the present, the .marine Diesel engine in America has been progressively developing—rather too rapidly for the limited personnel supplied the submarine service. The advance from the four-cycle to the two-cycle did not turn out a success. In the meantime several Diesel engine firms in this country developed very reliable four-cycle Diesel engines, and these types are to be installed in future submarines. When appropriate means have been found to carry off the heat from pistons and wrist pins of the two-cycle type, then the navy may return to that more-advanced machine and even to the double-action engines which are now under investigation and experimentation. If the high surface speed submarines continue to be considered a necessity, the demand will force the adoption of an engine which will develop more horsepower for its weight and size than does the four-cycle Diesel. Steam propulsion offers so many difficulties that the idea, although advanced and taken up by commercial firms, never got beyond the sketch stage.
While on this subject of development of submarine Diesel engines, a word for the navy personnel. The officers and men had already learned through sad experience the many difficulties encountered in helping to develop a new type of engine, the internal combustion engine—gasoline explosive engines. With this experience they went to boats in which Diesel engines of much less reliability were installed. They then had to learn a new type of engine and continue to help the designers develop it into a reliable submarine engine. This they accomplished through many breakdowns, often at inauspicious times. That the designers in this country have finally reached a reliable four-cycle engine for submarine use is largely due to the work of this handful of navy men; although during that painful interregnum when engine parts were being broken faster than spares could be turned out by the contractors, neither side was willing to concede anything to the other.
In overhauling engines in submarines, the very limited engine room space available was a very difficult handicap; the designer was limited in space and he took as much as he thought necessary; the need of more room to overhaul machinery finally won recognition.
In addition to engine trouble, storage battery difficulties came to bring added anxiety to the submarine personnel. The battery itself was sufficiently reliable; the greater trouble was experienced in the installation. It had to go inside a definite space and was assembled and put together in the boat and usually by men without sufficient expertness. The navy in the beginning did not possess men with expert knowledge in the care of storage batteries. They learned through experience, and when the personnel must learn in this difficult school, materiel naturally suffers.
With all the defects in motive power to contend with, hull defects added their mite. Some of these were due to design; to material used; but many more were attributable directly to an undeveloped system of hull overhaul. In addition, hull development was applied to the active submarines, requiring long periods at navy yards for necessary alterations.
During this transitory period the school for the submarine personnel was in the active flotilla; nowhere else could the officers and men learn the intricate machine which had been given them to operate.
No mention has been made of the weapon of the submarine—the torpedo.. The battleship, during this stage, with ample space at its disposal in large and commodious torpedo-rooms, could not boast of great success ; how much less chance had the submarine with practically no space for overhaul and fully occupied as it was in making a successful surface vessel out of itself.
The cycle of the submarine endeavor at that time was surface running, training in submerging, firing torpedoes, then overhauling everything, using inadequate facilities. Commanding officers (there was at this time only one officer in each vessel) had no time at their disposal for the study of the tactics and strategical qualities of their vessels, much less for their demonstration.
A submarine submerged is blind. At the surface it is enabled to see by means of its periscopes. The periscope is then the submarine's eye. We all understand the disadvantage of poor eyes. Our submarines have suffered considerably from this very vital defect. A submarine operating in the vicinity of surface vessels, especially in maneuvers with other types of warships, is at a great disadvantage if its eyesight is poor. The fact gives the personnel a persistent feeling of insecurity, and makes them prefer to keep to themselves.
The air within a submarine submerged for any length of time becomes exceedingly foul. Odors of acids, perspiration, men's breaths, etc., add their poisons to the air. There are many systems in use to purify the air of submarines. Some have been experimented with, but up to date none have been adopted and used as a standard type.
The navy uniform for submarines is the same as for the rest of the service. It has been demonstrated inadequate in cold weather. It is none too suitable in any weather. For winter operating, leather or some wind-shield substitute is required.
There remain many other features important to the submarine. In the development the big and more important defects have received first treatment. Others must bide their turn. Progress will be more rapid after the principle of "undivided attention." has been accepted, and the materiel and personnel administration in upkeep and development co-ordinated under a single head.
Two firms have built practically all the Submarines for the United States Government. The designs were furnished by the builders and approved by the bureaus of the Navy Department concerned. In some cases the operating personnel was consulted, but oftentimes the head of the submarine force was beyond reach and to consult him would delay the awarding of contracts. Characteristics were laid down by the Navy Department and incorporated in the specifications and plans. The interest of the builders was toward standardization in design and size. The Navy Department desired each class to be a distinct improvement over the previous one. It would have been better to have effected a compromise, as was done in England from the beginning of submarine development; lay down one advanced type with all improvements installed for test and repeat the advanced type of the year before. This single vessel each year to be rushed to completion in order to try it out in service before laying down duplicates. This excellent practice could be put into effect with the three 800-ton vessels appropriated by the last Congress.
VI. DIFFICULTIES
Until the war in Europe focused attention to the very great usefulness of an efficient submarine vessel, scant attention, even respect, was paid to the submarine and the personnel working it. Many high ranking officers considered the duty a waste of time and advised young officers in whom they took a personal interest to keep out of it. A great majority of young officers take their cue from the older and more experienced; in consequence, the feeling throughout the service, especially in the Navy Department, and on board the large ships, was not friendly.
The bureaus complained of the very large cost of upkeep. Engine spare parts are expensive, and a vast quantity of valuable battery material was destroyed' or ruined in .casualties, some of which were due to inexperience or inexpertness of personnel. The repairs to the hulls require workmen most expert ; this quality of work is high priced. The question was asked frequently by those having cognizance of the money expenditures "Arc submarines worth their keep?" Submarines were particularly annoying to the trial boards, due to frequent failures to make the required speed tests, necessitating delays.
The submarine's crew, when not operating, should be quartered where they can obtain plenty of sunlight and fresh air. The machinery requires the almost constant use of a machine shop. Space is almost constantly demanded to overhaul storage battery cells, to assemble new cells; and facilities to boost cells, to replace others. Torpedoes require a place for general overhaul outside of the boat, in order that the vessel meanwhile may maintain its submerged training. These fundamental requirements had been supplied, but as the flotilla grew, tender facilities lagged behind; the navy personnel was short of men to fully man vessels in commission. The complement of a submarine tender was found to equal the total crews of the submarines tended. This was an enormous overhead charge to pay for vessels which were not considered to be capable of important naval work.
The quality of the personnel itself was attacked; it was blamed for a condition that was not of its choosing. Officers and men were ordered to submarines in just the same way as to surface vessels; that is, without any regard to previous training or fitness. Many volunteered for the duty, and as applications were not very numerous, most of these were accepted and ordered. Even though the duty was known to be exacting in hard work, there were compensations acceptable to young healthy men ; greater responsibility for, rank, less rigid formalities of the service, watch standing only at sea, and an assurance of remaining in the country. These men blazed the way for others to follow, and they received mostly hard knocks in doing it. Their experiences have proved the importance of developing the submarine as a separate branch of the navy.
In any military service, rank is always an important factor. Rank had always been denied the, submarine.
Probably the worse feature of submarine service occurs when a submarine is obliged to go to a navy yard for, overhaul without its tender. This occurs very frequently. It is assigned .a berth in the same way as would a vessel capable of housing its own crew, for instance, a. destroyer. The crew are assigned berths or billets on board the receiving ship, usually some distance away from the location of the submarine. The submarine crew at once chafe under receiving ship discipline. The character of their work keeps them in dungarees all day: When they return to the receiving ship they feel the implied, though not always expressed, hostility of petty officers, and sometimes officers, towards them for being dirty themselves and for dirtying decks or paint work. The officers put up with greater discomforts; they are required to keep up their paper work without yeomen or office facilities. They must beg or borrow the use of machine tools. Altogether the conditions are most trying and are not, conducive to a close co-ordination of effort. Rather than go to the receiving ship a custom has grown up to "board around" on hoard destroyers where the atmosphere is congenial.
This attitude of mind is characteristic of the navy: Many can remember, the open hostility between the deck and engineers. The war has raised the submarine higher in the navy's opinion; however, the submarine service knows it cannot flourish while mixed in the Stew with other types. It is as distinct as an aeroplane and far more difficult to run efficiently. The aeroplane is to have its distinct and separate organization. Is our submarine service of less importance to the country?
VII. BASES AND TENDERS
The machinery and outfit of submarines is so vastly different from those of other warships that facilities for repair and upkeep should be separate from that of surface vessels. This has been demonstrated at every stage of their development.
If our submarines are to be of a .mobile type, but few separate bases are needed, located at strategic points. For operations in distant areas sufficient tenders are required.
At these bases schools of instruction and training should be located. It must be remembered that we shall require a large number of trained officers and men to man even those submarines already provided, and the prospect is for large additions in the future. Previous training will avoid many of the difficulties experienced in the past.
.All officers and men on duty with aeroplanes are now considered on sea duty. How much more justly this rule should apply to the personnel on duty with submarines, even though they may be living ashore except when actually operating. The duty in submarines is sea duty of the most arduous kind and cannot be made continuous for that reason. Nations at war keep double crews for each submarine.
VIII. STRATEGY
Command of the sea is a term employed during a war to define the naval power of a belligerent which by means of its more formidable sea power is able to use the sea with reasonable security and deny it absolutely to its enemy.
In the past the instruments of sea power have consisted of surface warships. New instruments now exist—the aircraft and the submarine. Air power can be overcome by superior air power. Undersea power cannot be overcome by undersea power alone. To destroy this new power, fast surface vessels and aircraft offer the best chances of success.
Command of the sea includes the control of the surface of the sea. This control prevents surface craft of an enemy using the sea. This is the first essential step to the destruction of undersea power. In this latter work many speedy vessels are used, armed with rapid-fire guns, mines and submarine nets and accompanied by aircraft; it resolves itself into a hunt for a type of vessel that can in an instant disappear from view and appear again miles away, or else can remain in the vicinity of discovery with but a single, almost invisible, eye above water, ready to launch a torpedo at the vessels engaged in the search.
The submarine makes long passages on the surface. It submerges so as not to betray its presence. Submerged radius is but a very small percentage of its total radius of action. Submerged radius, however, can be regained after being used by recharging batteries.
The origin of most wars between nations is commercial. The naval aim in war is the command of the sea. By the sea the sinews of war are to a large measure obtained. To this end the enemy's fleet is the point of attack. The destruction of the enemy's sea power usually decides the war in favor of the victor.
If one belligerent is inferior in surface vessels to an extent insuring defeat if it meets the enemy fleet, then that. Belligerent concedes command of the sea temporarily to the enemy.
The submarine is the weapon of the weaker belligerent. It continually points a dagger at the heart of the stronger fleet; provided that fleet actively enjoys its command of the sea.
The stronger belligerent, the one commanding the sea and controlling the surface, will hesitate to send its vital ships to sea in face of the menace of the enemy's undersea power, unless its margin of superiority is very great.
We are thus brought to this condition: Two belligerent naval powers each with formidable surface fleets, holding them in port, fearing in the case of the stronger, the enemy's undersea power and in the case of the weaker, the enemy's surface power.
The dispute for the command of the sea now begins; the stronger belligerent using surface warships only, the weaker, submarines only. Meanwhile the great fleets of capital ships remain spectators to the struggle of their champions, the one to maintain the security of the sea for their vessels and the other to destroy it. One can readily understand the necessity of the most effective submarine type for a weak sea power.
Against a convoy of merchant vessels, transports, and auxiliaries and against a large fleet of warships in passage across several thousand miles of sea where fuel in all types must be economized by steaming at reduced speeds, the submarine offers itself as a most effective offensive weapon.
A nation weak in capital ships and therefore unable to maintain a threatening naval force upon the flank of an advancing enemy should be able to rely upon an effective submarine offensive.. With mobile types a dangerous sea area can be made for an enemy. When he enters this area he will be navigating in the Vicinity of numerous uncharted rocks—the submarine. If the weaker nation owns high-speed battleships, capable of tracking an enemy fleet without being brought under superior gun power, these submarines can all be concentrated upon the enemy.
IX. TACTICS
Tactics deal with the actions of submarines in the presence of an enemy. Upon sighting An enemy the submarine must submerge. Surprise makes up for its lack of high speed when submerged. It must be capable of submerging quickly. It should be able to observe the enemy without discovering its own presence to the enemy by surface commotion. It must have a good clear pair of eyes to see distinctly, and it must be armed with weapons capable of 'destroying the largest enemy with a single hit. Speed submerged is a ,necessity for successful attack; the submarine must reach a range where a miss is impossible, for the number of its torpedoes is necessarily limited. Radius submerged, in time or distance, should be large, to permit the submarine to continue its attack as long as necessary and afterwards to escape from chasing vessels.
A submarine cannot .be blockaded in port unless the water should be too shallow for it to totally submerge. The battleship and other warships of moderate speed must be continually on the lookout for the wake of a torpedo, and they will be unable to avoid the blow if truly aimed. The speedier warships must utilize their high speeds to insure safety, yet there will be times when they will be caught at slow speeds or stationary by a roving submarine.
With the development of the offensive submarine, nations with surface fleets will hesitate to claim full command of the sea.
Tactical principles of concentration apply equally to submarines. The radio can direct a concentration of submarines as readily as it can direct destroyer concentration.
The menace of the submarine has already surrounded a battle fleet with a cloud of destroyers and trawlers. Further submarine development may shake the world's confidence in the ability of heavily gunned and armored ships to retain command of the sea. If they refuse the risk involved and remain in port while other vessels perform their duty, is not the price more than a nation might be willing to pay?
In the case where two belligerent surface fleets are so equally matched that they are each seeking to engage, the part the submarine will play in the battle will he difficult to accurately determine. This is the condition that was in the minds of the advocates for fleet submarines. The moderate surface speeds of submarines would prevent them from gaining advantageous positions for submerged attack; destroyer speed would be necessary for this. Great difficulty might be encountered in recognizing friend from foe after submerging. Submarines would be in danger of being rammed or shelled by both sides indiscriminately. It is said, even destroyers suffered this disadvantage in recent battles in Europe. One plan might be to use them in a definite area before the action or after action upon the enemy's normal line of retreat. If possible, submarines should be present when the battle takes place.
X. SIZE
Even the rankest doubter is now convinced of the value of an effective submarine. However, we are very widely at variance over the type we should build.
It is most difficult to decide where principles already understood for one type should be applied in the evolution of a dissimilar type. Some years ago there were serious proposals to build two types of destroyer; one of small size for coast defence and one of large size to go with the fleet.
In building any type of warship consider the maximum service the type may he called upon to perform.
Small size, short radius submarines fit into a passive defensive plan of employment; to fight the enemy after he arrives practically in sight of our coast. As our coast line is very long, numbers are an important feature in such a plan. Might not a commander-in-chief decide to employ his submarines in an advanced position? If he did so decide, he would be unable to carry through his plan.
Many of those who advocate the small submarine still desire it to perform service for which it is incapable, due principally to size, giving limited space for stores, fuel and other necessities.
From the standpoint of normal evolution can we place a limit upon displacement? How can it be said, without a glance into the future, that a submarine of a certain tonnage will fulfill our requirements? Submarine growth cannot be regulated in that way.
XI. THE PRINCIPLES OF UNDIVIDED CONTROL
When the submarine appeared in our navy, more or less in the shape of a large torpedo, it is said that a proposal to turn it over to the Bureau of Ordnance was seriously considered. If the torpedo with which we are working to-day had been divided up among the bureaus, would the torpedo be as satisfactory? However that might be, it is evident from past difficulties and present development that no harm to the submarine can come if we place the responsibility upon the shoulders of a single individual and give him the responsibility and the money power to develop the type of submarine capable of performing the duties called for in our naval war plans. We cannot get away from the truth that both the submarine and the aeroplane require individual attention and cannot thrive in close contact with sturdier, well-developed types of warships.
In view of the importance of the submarine to a comparatively weak sea power, counciling prompt and scientific treatment, would not a closer co-ordination of all those who are designing and developing this type be a reasonable solution?