Protection Against Underwater Attack
By Lieutenant T. L. Schumacher (CC), U. S. Navy
Introduction
The object of this article is to bring to the attention of the naval service a question of vital and increasing importance, which, it is believed, is not at present receiving the serious consideration it deserves from everyone interested in the efficiency of the Navy. Suggested courses of action are submitted with a view of directing thought on this important subject, but the writer realizes that the solution will result only from the combined attention of both the design and the operating groups of the service.
There is no attempt, either veiled or open, to introduce the much discussed line-corps question. The writer has no desire to enter into this controversy. If any statements are made, conclusions drawn, or courses of action suggested which appear adversely or favorably to criticize any particular group of the naval establishment, the reader is requested to maintain the same neutral attitude which, it is believed, the writer has maintained in preparing this article.
Historical
The advent of iron, power-driven ships some sixty years ago produced a subtle change in the standard of naval warfare. The drawn out, hand-to-hand fight of the day of John Paul J ones was replaced by the artillery duel where action was quick, and victory or defeat was· decided in a single stroke. In the day of that great hero victories were frequently won by the stubborn resistance of a crew on a seriously damaged vessel. With the new form of fighting injury became catastrophic. The vessel was sunk by a single well-aimed blow of the enemy. The crew was not given the opportunity to continue the fight, once the ship was severely damaged. Defeat must be accepted. The standard of resistance was lowered. This change is aptly expressed in the paraphrase "Wooden ships and iron men, and iron ships and wooden men." The very plan of battle was altered to suit the new conditions; as shown by the great emphasis put on the advantage of delivering the first blow.
But history is repeated, and once again a crew of "iron men" may keep a ship afloat and fight her to victory, after she has received the full attack of the enemy, and sustained an injury which, but a few years ago, would have been considered mortal.
Two recent developments of naval warfare which have taken place within the last two decades are exercising a profound influence on the construction and handling of warships. These developments are:
(a) The increased effectiveness of torpedoes and mines as offensive weapons.
(b) The increased ranges at which ·main battery guns may be accurately fired.
Increased Effectiveness of Torpedoes and Mines. Torpedoes proved their worth as practical offensive weapons, under wartime ranges and conditions, for the first time in the late war. Mines, previous to that war, had been used only as weapons of defense. The World War, however, saw them very successfully and effectively used for offensive action.
Increased Ranges of Main Caliber Guns. The development of fire control and airplane spotting has shifted the limitation of range from the control to the gun. Up to a few years ago our guns were better than our control; that is, we could shoot farther than we could aim. Our control is now better than our guns; we can aim farther than we can shoot. Battle ranges are, therefore, the maximum ranges of the guns.
These two developments are matters of common knowledge. They are familiar not only to the naval profession but to the general public as well and therefore require no general discussion.
Exposition
An enemy's attack may be met by two methods; defense and protection. By defense is meant those measures whereby his attack is checked before it matures. By protection is meant those measures whereby his matured attack may be received without serious injury. A well-directed attack of a powerful enemy canbe met successfully only by the use of methods of both defense and protection. Man instinctively resorts to defense first; protection is always a secondary measure. The development of methods to overcome the danger of underwater attack has followed this rule. We have developed defensive measures, such as high speed, accurate and rapid fire of secondary battery, camouflage, depth bombs, mine sweepers and paravanes to a high degree of efficiency; but the development. of protective measures has been given little consideration by the Navy as a whole. Although we have considerably reduced the danger of underwater attack by reducing the chances of its maturing, we have not greatly reduced the danger if the attack does mature. In this article it is proposed to discuss this rather neglected question of protection against a matured underwater attack.
This discussion will be confined to capital ships. Much of it also applies to ships of all classes, but the particular requirements of each class are beyond the scope of this article.
Underwater attack is a reality. Torpedo and mines are offensive weapons which an enemy will utilize whenever possible. We must, therefore, provide our ships with as efficient a protection against this attack as possible. Some form of protection is now being incorporated in the latest capital ships of all navies, and its importance is indicated by the fact that it is now considered as necessary by the designer as the above water protection against shell fire; that is, the possibility of the loss of the ship from underwater attack is now as great as the loss from gunfire. Underwater protection differs from above water protection in three respects, as follows:
(a) Adequate armor will stop a shell at or very near its point of impact, but at present there is no known means of keeping an explosion from entering a vessel once the torpedo or mine has exploded against its shell.
(b) Protection against shell fire is, in most cases, one hundred per cent efficient if the shell is kept out of the vital parts of the ship. Underwater protection must, to attain this efficiency, not only keep the explosion out of the ship's vitals, but it must also be so designed and operated as to keep the resultant entrance of water from the ship's vitals, as well as to maintain to a certain degree the seaworthiness of the vessel after the explosion has occurred. Damage by shell fire near the water line takes the nature of underwater attack in this respect, and is included as such in this article.
(c) Protection against gunfire is almost entirely passive; that is, the armor is built into the ship and it affords the necessary protection without any action on the part of the ship's company. On the other hand it follows from (a) and (b) above that protection against underwater attack, to be effective, must be operated properly by the personnel on board at the time and immediately after the attack occurs.
The operating group of the Navy has been well trained in the method and theory of protection against gunfire. This protection requires no routine action on the part of the ship's company. As this protection was the only common form on ships up to the past few years, we have grown into the idea that all protection is passive. The idea that protection, to be effective, may require action on the part of the ship's personnel is a new one which, it is believed, has not yet been generally received by the naval service. The ideal protection is one which operates automatically when called upon, and perhaps the operating force may feel that the designer has not fulfilled his mission until he produces a protection against underwater attack, which, like armor, may be built into the ship and then forgotten. Forms of underwater protection which operated automatically have been designed and installed, but have been found to possess such serious objections in practice that they have been discarded. The designer has so far been unable to produce a successful automatic protection against underwater attack, and the latest designs in all navies are based on the principle that the ship's personnel will operate the devices installed, when they are called upon to offer protection against attack. It is not believed that the operating group appreciates this basic principle, nor accepts it as an actual condition, which it is.
Discussion
The following steps are necessary if our ships are to be capable of properly resisting underwater attack:
(a) The importance of underwater protection must be properly appreciated both by the design and operating groups of the Navy.
(b) The designer must meet, so far as possible, the demand for adequate protection, and equip our vessels with the necessary material and devices for its operation.
(c) The design group must furnish to the operating group all information as to the principles of operation of the devices installed, and the necessary data for their efficient operation.
(d) The operating group must completely understand what protection is incorporated in the design, what its principle of operation and limitations are, and must be able under all conditions properly to operate the devices installed.
The Importance of Underwater Protection. A realization of this may better be obtained by an understanding of what effect underwater damage has on a vessel. This effect may be broadly divided into two classes:
(a) The vessel will lose some or all of her buoyancy. In the latter case she will, of course, sink.
(b) The vessel may lose some or all of her stability. In the latter case she will, of course, capsize.
With modern designs the reserve buoyancy is so great that it seldom occurs that sufficient water is admitted entirely to destroy the ship's buoyancy. Indeed, even an extreme loss of buoyancy alone has no serious effect on a modern battleship, other than slightly reducing her speed, somewhat decreasing the efficiency of her armor and, under some conditions, slightly reducing her seaworthiness.
The stability of a vessel is, however, a quality which is more susceptible to damage. In nearly every case of underwater damage the ship, if she does not capsize, at least takes a more or less serious list or severe trim. We will, therefore, confine our attention to the effects of lost stability.
These effects may be broadly classified as:
(a) The ship lists over so far or takes such a severe trim as to become either unmanageable or unseaworthy.
(b) The ship's transverse metacentric height or range of stability may be so reduced as to render her unseaworthy or cranky.
(c) The ship may take a moderate list or trim which does not seriously impair her seaworthiness but greatly reduces her fighting efficiency. By moderate list is meant a list of not more than twelve degrees.
(d) There may be a combination of (b) with either (a) or (c). List and change of trim may, of course, occur simultaneously.
In case (a) nothing can normally be done to save the ship. However, as will be shown later, these effects are rarely produced directly, by even two torpedoes or mines acting simultaneously. Also, with a proper design, effect (b) is rarely so pronounced as to be dangerous.
Result (c), that is a moderate list or trim, is by far the most common effect on a naval vessel, and is therefore the one demanding most consideration.
What effect has a moderate list on a ship? In time of peace, although it may be great enough to influence her seaworthiness somewhat, the situation is not serious, and, if she is properly handled, no harm will result other than making her a very uncomfortable vessel for the personnel on board. It is the effect on her fighting efficiency which requires much thought.
In time of battle a vessel stands at least an even chance of receiving a torpedo or mine on the engaged, rather than the un-engaged, side. Battle ranges of the future will be the maximum gun ranges. A battleship in action is torpedoed (or mined) on her engaged side, as a result of which she takes a moderate list of, let us say, eight degrees. The maximum angle of elevation of the guns relative to the horizontal is decreased by the angle of list. The maximum range is thereby decreased by about two thousand yards. Her speed is slightly reduced under the list. Under such conditions an enemy vessel of the same, or even somewhat less, normal fighting power can choose her own range, stand-off beyond the reduced range of our listed ship, and dump any number of salvos into her with perfect immunity. The enemy's action will, of course, be determined by the nature of the battle, whether it is a fleet action or ship-to-ship fight, but in any case our listed vessel is at his mercy. We may imagine our vessel to be manned by the most efficient captain, the four best turret crews, arid the best engineer's gang in the world, and her fighting efficiency under such conditions 'would still be practically zero, merely because of a moderate list of eight degrees. The cost of the ship, the time and energy spent in training her crew, are wasted and, more important, the ship is lost and our fleet is weakened because she has received an injury which in itself, would mean nothing more than a slight inconvenience to her crew. Does not this picture alone convince us of the importance of the problem of underwater protection?
The above discussion presents the most serious effect of a list because in battle time it is the all-important element. If such a condition obtains for only a few moments the ship may be lost. In battle, then, the ship must be righted immediately.
It is not contended that such will always be the result of a list in time of battle. The range may be such that even a severe list will not bring the guns below the necessary elevation. The vessel may receive the underwater damage on the unengaged side; or, if received on the engaged side, she may, in rare instances, be able to reverse her course, thus presenting her high side to the enemy. But the disastrous conditions described above may obtain. Is it not too serious a matter to leave to chance?
The ship's fighting efficiency will be reduced by a list, in the following respects, whether the list be toward or away from the engaged side:
(a) Ammunition is difficult to handle and guns hard to load. The rate of fire will, therefore, be reduced.
(b) The nature of the ship's roll may be considerably changed, thereby reducing the accuracy of director fire.
(c) Defense against submarine attack on the high side may become ineffective at short ranges, because the secondary guns could not get down to the target.
(d) The efficiency of the armor protection is reduced. If the list is toward the engaged side, the vertical armor becomes submerged and the decks, which are not armored to receive the impact of a large caliber shell, present a considerable projected area to the trajectory. A list away from the engaged side, even though moderate, may, in rough weather, bring the lower edge of the vertical armor above water, thus exposing the unprotected side to direct impact.
(e) Much of the machinery operates partly: by gravity, with a list this force is displaced from its normal line relative to the ship. As an example the water surface in the boilers will be inclined, which may even uncover some of the heating surfaces. The weights of all moving parts will be thrown on bearings in abnormal lines, which will result in decreased speed of operation or even in completely disabling the mechanism. These results will, of course, be felt whether the ship is in battle or not, but in the latter case they may be reduced by proper care and attention in operation, while in time of battle no such attention may be given without disturbing the ship's fighting organization.
These difficulties and many others may be appreciated properly only by one who has attempted the various routine operations on a vessel listed even to so small an angle as five degrees.
Concluding, as we must, that a list is liable to be encountered in battle, and that it may, even though moderate, result in the loss of the ship and certainly will considerably reduce her fighting efficiency it becomes absolutely necessary that a means be provided for reducing a list quickly and efficiently under battle conditions.
The. designer must meet the demand for adequate protection.
It is not deemed desirable to discuss this requirement in detail in this article. In general, underwater protection operates in three ways:
First - To restrain the explosive forces from entering the vital parts of the ship. As stated above the explosion cannot, by any known practical means, be confined to the point of impact. Obviously, then, the vital parts of the ship must be removed from the point of impact. This is done by withdrawing the vital parts from the ships’ side, and stowing, in the intervening spaces, material which can be lost in action without affecting the fighting efficiency of the vessel. The construction of these side spaces must be such as to absorb the force of the explosion. The material stowed in them may be relied upon to increase their capacity in this respect.
Second - To restrict the inflow of water, after the explosion has been dissipated, to a minimum space. This is accomplished by the division of the ship's underwater body into small watertight compartments.
Third - To provide means for draining and flooding compartments, so as to keep the ship erect. This is accomplished by the proper flooding connections, drain lines and pumps. Whether or not the present installations are sufficient and satisfactory must be decided by the operating force.
The methods of accomplishing these purposes are not a perfect development. Much progress is yet to be made. However, at present, a capital ship will withstand two torpedo or mine explosions and still remain afloat very nearly upright (within twelve to fifteen degrees), and fairly seaworthy. For this reason it may be said that the stability effects (a) and (b) above, will seldom be encountered; that is, a modern capital ship will seldom, if ever, list over so far, as to become unmanageable; nor will her stability be so much reduced as to make her unseaworthy, as the direct result of a torpedo or mine explosion. Examples may be presented which appear to contradict this statement, but in all such cases the disastrous effects have been caused by events secondary to the explosion proper. This will be discussed later.
Briefly, then, we may say that, so far as the probability of the vessel's being lost from the direct effects of a torpedo or mine our protection has been made automatic, and requires no attention of the ship's force other than to see that it is kept in proper condition.
The design group must furnish to the operating group all data necessary to the operation of the protective devices installed.
Besides a general statement of the operation of these devices, the following data should be furnished in the form of readily accessible graphs and sheets:
1. Size, location and use of all compartments.
2. Flooding and drainage connections to all compartments.
3. Time required to flood and drain all compartments.
4. Sequence of compartments as regards availability for flooding.
(For example certain storerooms should not be flooded except as a last resort.)
5. Resultant change of mean draft, list, and trim due to flooding each compartment.
6. Resultant change of transverse metacentric height and range of stability due to flooding a compartment if such change is of serious magnitude.
7. Location and means of operation of all flooding and drain lines, pumps and valves.
8. Means of access to al! compartments, both under cruising and battle conditions.
9. All doors and hatches to be closed, and routes of passage to be followed in time of battle indicated.
The operating group must understand and be able properly to operate the protection installed. This requirement can be met only by:
(a) Having a recognized group to perform these duties, with a properly indoctrinated officer at its head.
(b) Training and drilling this group into an efficient organization, in which each man realizes his responsibilities, knows. his duties, and understands the general method of operation of the whole system.
The duties of such an organization have fallen to the first lieutenant. It is suggested that, whatever position the head of this group occupies in the ship's organization, he be known as the "stability control officer" in the battle bill, and his group be known as the "stability control group." The stability control officer should be familiar with all parts of the ship, and should particularly appreciate his responsibilities in battle. He should be familiar with the graphs and sheets containing the data enumerated above. He should have a permanently located battle station. In this station these graphs and sheets should be so arranged as to be instantly accessible. He should not be required to leave this station in time of battle except in extreme cases.
The mission of the stability control officer should be to keep the ship afloat and on an even keel in time of battle, and no additional duties, such as taking charge of topside casualties, should be assigned to him, if they interfere with this mission.
It is suggested that an officer familiar with ship design and construction, buoyancy and stability, and the theory and practice of water-tight division, would be best suited to this duty.
The stability control group should consist of enough men so that one man could be assigned only as many valves, lines, or pumps, as he could properly and expeditiously operate. The men of this group should be chosen carefully with a view to picking only those who would appreciate their great responsibility. These men would have to operate under remote supervision; consequently only the most reliable should be put on these stations There should be a separate interior communication system, connecting all stability control posts with the stability control station. This system would be the only regular medium of communication between these points.
The battle duties of the stability control group should be supplemented by cruising duties. When cruising in time of war in dangerous waters, a skeleton crew should be on watch at all times, to see that the designated doors and hatches be kept closed, and also so that immediate steps could be taken if the vessel were torpedoed or mined.
The proper training of such a stability control group will be a very difficult matter. Each man must be able to find his way about his part of the ship and operate the valves or pumps assigned to him under all conceivable conditions. The control officer could become proficient in his duties only by long and conscientious study and application. The group should be drilled, individually and as a unit, daily. These drills should be supplemented by occasional actual battle condition drills. It is suggested that it be made a part of the battle efficiency inspection to flood compartments without previous knowledge of the stability control officer, and the time taken, and the method and efficiency in bringing the ship back on an even keel, be given due consideration in determining the vessel's general fitness for battle. This suggestion will be entertained with some apprehension by the average commanding officer; but, if the idea that a vessel may be partially flooded and still be safe, is to be accepted, no better way of growing accustomed to such a condition can be suggested. It is believed that this very apprehension is an indication of the necessity for such a drill. If we cannot safely right a ship under the ideal conditions of drill, how will we ever do it under battle conditions, when the attention of the commanding officer and most of the ship's company is of necessity engaged with other matters? Efficiency in gunnery is attained by gunnery exercises; efficiency in underwater protection can be attained only by flooding exercises. The thought that the ship's side is a deadline beyond which bodies of seawater must never pass, must be dispelled if a satisfactory underwater protection is to be developed. Such a drill could not, of course, be attempted until the stability control group becomes a thoroughly efficient organization, through preliminary simulate drills.
The stability control officer could only fulfill his mission in battle if he were made solely responsible for the integrity of the watertight division of the ship. It is believed that the importance of the integrity of watertight bulkheads and decks is not generally appreciated, although conditions have certainly greatly improved in this respect in the last five years. The experiences of many vessels in the World War testify to the fact that boundaries of watertight compartments have not been regarded with the proper respect. Every man in the crew should be warned of the dangers of cutting even a small hole through one of these boundaries.
We are inclined to mistrust the strength of watertight bulk heads, and have made it a part of the battle drill to supply temporary shoring. Bulkheads are built sufficiently strong to withstand any pressure ordinarily met with, and it is suggested that some effort would be saved by giving this phase of the question less attention.
Bulkheads and decks are of necessity pierced by doors and hatches. These openings, when not properly closed, destroy the integrity of the boundary which they pierce. This serious question has been partially settled by reducing the number of these openings to a minimum, many times at the expense of efficient operation in cruising condition and the convenience of the operating force. The openings installed are all provided with suitable means for closing them watertight. If the necessity for making the stability control officer responsible for the proper operation of watertight doors and hatches, and the placing of a crew of men on these openings in dangerous waters, is doubted a review of the reports of casualties during the World War will remove this doubt. It is remarkable how many of these contain such statements as "The water spread to the adjacent compartment due to leaks through the watertight bulkhead" or "Watertight door (or hatch) number--could not be closed properly, and compartment number--was flooded." These same bulkheads and doors were put to a · much more severe test when the ship was built than they underwent at the time of the casualty. Why did they not perform their functions properly when called upon in service? With the stability control officer put in complete control of this question, it is believed that such reports would be less frequent, and lost ships in time of war less numerous. The evidence in almost every case of the loss of a capital ship by torpedo or mine in the World War indicates that the loss was not due to the direct effect of the explosion itself, but was caused by these secondary effects which would not have resulted if the integrity of the watertight boundaries, had been maintained. It was not maintained in some cases due to improper design; in other cases due to improper operation. It is believed that defects in design have been greatly reduced in the later ships. Has the standard of operation also been raised?
With such an organization as the stability control group, a modern man-of-war will be well nigh invulnerable to any torpedo or mine attack likely to be met in the war of the future. The almost irresistible power of underwater explosion will be dispelled, and the grave fear of mines and torpedoes experienced by every seaman in the late war will become a thing of history. Unless some such measure is adopted, however, underwater attack will, in the near future, attain such a degree of efficiency as to enable an enemy, under favorable conditions to render a whole fleet helpless without firing a gun.
We preserve and cherish Lawrence's familiar order, but it has lost the meaning which he put into it. We hear it frequently quoted, but, with few exceptions, it is applied in a figurative sense. But once more a vessel may be all but lost, under the power of the enemy's underwater attack, and yet be kept afloat and fought to victory by the "iron men" aboard of her. To the crew of such a vessel will be revealed the glorious old meaning of the words - "Don't Give up the Ship."
Conclusion
Some of the courses of action suggested in this article are already being followed, at least in part. They have been incorporated in the discussion so as to maintain continuity. The suggestions as to new methods and courses of action have been made with some hesitancy. It is appreciated that they are incomplete, and the details perhaps not entirely practicable, due to conditions not familiar to the writer. The suggestions are made in. the hope that they will cause some additional consideration to be given to this subject by the naval service in general, and form a basis for further discussion. If this hope is realized, the object of this article will have been attained.