DISCUSSION.
"OUR NEW BATTLESHIPS AND ARMORED CRUISERS." See No. 96.
Lieut. W. L. RODGERS, U. S. N.—After describing the contrasting features of the Virginia and Maryland, Mr. Taylor's paper concludes by asking the service several questions in regard to the choice of types.
These questions can be answered only after coming to some conclusions as to the tactical value of each increment of one knot's speed. Or in other words, we must have an approximate idea as to what weight of gun-fire is the equivalent of one knot of speed. The subject is thus to be regarded from a tactical standpoint.
I shall make three or four tactical premises from which and from the data on design given by Mr. Taylor, I shall endeavor to draw some conclusion as to the highest speed necessary for battleships. Of course, if the tactical premises are in any degree erroneous, the conclusions are proportionately valueless; but if by discussion and comparison of views we can ascertain that certain tactical ideas are generally acceptable, then I think we may trust our deductions based upon them as to proper speed.
It seems clear that between two hostile ships or squadrons similarly armed and protected which are maneuvering for effective position for the best use of their weapons; the advantage of one knot's superiority of speed becomes less as the speeds become higher; for the reason that each adversary can move more quickly to escape from a position of tactical inferiority.
Moreover, the more quickly the vessels move, the more difficult it will be for a captain or admiral to perceive and seize the fleeting opportunities which offer themselves for the proper employment of the advantages which undoubtedly lie in superior speed.
It must also be remarked that each successive knot of speed requires an ever increasing sacrifice in the weights devoted to battery, ammunition and armor.
Another important point is that the more equally the fire of the battery commands all points of the horizon, the less tactical advantage is conferred by a given superiority of speed; since change of relative position entails less relative change in effective gun-fire. The difficulty is thus to decide upon the approximate speed at which the tactical superiority of maneuver conferred by an increment of speed is counterbalanced by the necessary sacrifice in the weight of broadside and protection.
Let us take the Virginia as a standard and ascertain approximately what changes in her armament correspond to variations in her speed.
Mr. Taylor states that her machinery weighs 1800 tons; develops 19000 H. P., and gives 19 knots speed. His figure 4 shows the H. P. necessary for reduced speeds of the Virginia and Maryland. He mentions also the greater weight of hull in the Maryland on account of her greater length. From these data I have made up the following table which roughly shows the weights available for combatant purposes corresponding to variations in the maximum speed.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 |
| Ship. | Maximum Speed. | Displacement. | Armor, Battery, Ammunition. Weights. | Amor, Battery, Ammunition. Weights. | Amor, Battery, Ammunition. Percentage of weights of Virginia. | Relative efficiency of armament compared to that of Virginia. |
1 | Modified Virginia. | 13 | 14,600 | 395 | 6217 | 129 | 149 |
2 | " " | 14 | " | 485 | 6127 | 127 | 145 |
3 | " " | 15 | " | 610 | 6000 | 124 | 141 |
4 | " " | 16 | " | 755 | 5857 | 121 | 136 |
5 | " " | 17 | " | 970 | 5643 | 118 | 130 |
6 | " " | 18 | " | 1260 | 5353 | 110 | 120 |
7 | VIRGINIA | 19 | " | 1796 | 4817 | 100 | 100 |
8 | Modified Virginia. | 20 | " | 1950 | 4370 | 90 | 84 |
9 | " " | 21 | " | 2100 | 3900 | 80 | 66 |
10 | " " | 22 | " | 2265 | 3400 | 69 | 45 |
The figures in column 7 marked "relative efficiency of armament" are based on those in column 6 and on the assumption that the general fighting efficiency of guns and protection will vary in a greater ratio than that of the weights actually devoted to the whole system adopted. Although the figures in column 7 are somewhat conjectural representing only an individual's opinion, yet figures lend themselves for comparison readily; and we have a convenient approximate scale to compare a little later, the tactical value of different maximum speeds.
From a tactical standpoint superior speed may confer on a combatant a relative advantage of position with regard to the use of each of the three arms, gun, ram and torpedo.
With regard to gun-fire superior speed coupled with superior target practice enables a ship to hold that range at which the superior skill is most effective. Equal speed will prevent the enemy from closing. If one needs speed to close, it is because the shooting is inferior at long ranges, and it would be better to devote efforts to target practice before the war, rather than build with a high speed to make up for defects in drill.
Superior speed may also be used to occupy and endeavor to hold a position such that the maximum gun-fire of one vessel is opposed to the minimum of the other. This problem merits examination.
Let us consider two ships of the usual battery of our service consisting of two heavy turrets on the midship line, some eight-inch turrets and a broadside battery of 5-inch or 6-inch guns, such as the Indiana, Kentucky and Virginia. In all these ships the maximum fire covers eight points on each broadside; four points forward and four abaft the beam.
In all, the minimum fire is about two points on each bow and greater and, except in the Kentucky, there is a heavier fire fore and aft than in a direction two points from that line. In none does the minimum fire vary much from 60 per cent of the maximum.
[DIAGRAM]
The diagram represents a situation where F (the fast ship) brings her whole broadside against S's least fire. This situation may be maintained by F if both ships circle about the point C. With speeds proportional to their distances from C. Or it may be maintained if F shifts her helm so as to follow a wave line course ahead of S. The latter plan would interfere with the fire of the six-inch battery as regards rapidity.
In the first case the speeds must be as 13 to 10 for F to maintain his superiority. Any less difference will be useless to F; more will be superfluous. If the arrangement of battery of F is altered so as to allow her to cover ten points on each beam with her maximum fire instead of eight points it appears by reconstructing the diagram that a superiority of 10 per cent of speed will do as much for as 30 per cent would do with a smaller arc of maximum fire. But it must be recollected that a turn of the helm on the part of S will bring his maximum fire to bear, so that while a superiority of 13 to 10 in speed is the least that can be useful to F, the possibility of employing it effectively depends almost entirely upon S, and upon his committing most unlikely errors in judgment. Turning to column 7 of the table, and taking 15 knots as the speed of S and 20 knots as the speed of F, these being in the ratio of 10 to 13; we find that 60 per cent of the efficiency of fire of S is equal to the whole efficiency of F. If the data and arguments on which the table is based are reasonable, it appears from it that under the circumstances most favorable to speed it will be impossible that a battleship faster than 15 knots shall compensate in action by her speed for her sacrifice of guns and protection. This statement does not mean that 15 knots should be the limiting speed for battleships.
[DIAGRAM]
For the use of the torpedo between battleships little is to be gained by high speed; because although it may be used to attempt to gain a position of advantage the slow ship has only to turn so as to bring her adversary abaft the beam when her own torpedoes are more favorably situated than those of the fast ship in case the latter persists in his approach.
For ramming, superior speed is essential, because a position suitable for a ram attack must be occupied before actually committing oneself to it. That is, the vessel about to ram must be so placed before attempting it as to make it almost impossible for the enemy to turn stem to stem, and so to collide with equal chances and fortuitous result. Thus favorable positions for ramming are mostly abaft the opponent's beam and so superior speed is necessary in order to reach him.
Let us assume that a superiority of five knots is necessary to strike an effective blow from astern. Let us also assume that the extreme range for effective shooting is 5000 yards. If then, a vessel tries to ram a battleship the latter will have half an hour in which to disable the former while she tries to approach from astern.
To get some idea as to the time-effectiveness of gun-fire, let us consider the battle of Santiago. In this action, an hour of firing destroyed the Spanish fleet at ranges which were never short and with shooting which seems not to have been good. The efficiency of armament of the Indiana considering her date of design and other features is probably about 75 per cent of that of the Virginia. From the results of the battle it seems probable that a superiority of 60 in column 7 of the table would enable a battleship to destroy her adversary by gun-fire in the half hour necessary for the latter to advance from 5000 yards to collision.
Under these conditions we see from the table that the necessary 5 knots' superiority in speed will cost too much in armament when the slow vessel's speed is as high as 16 knots.
If the above line of reasoning is even approximately correct, our new battleships have a much higher speed than can be utilized in battle to obtain 'tactical advantage. We must not conclude therefore that fifteen or sixteen knots is sufficient; for we must recollect that speed is a strategic factor, and when superior it confers the ability to force or refuse a battle, and to escape when defeated. But as battleships are not built to run away, but are meant for fighting, I think a speed barely equal to that of other navies is quite enough. Examples from history show that for attack a fleet is as fast as its fastest ships; yet for retreat it is no faster than its slowest ship.
So if our battle fleet is slightly inferior in speed to our adversary the latter will never be able to get away without fighting, if once it is sighted. The fact that if our ship tries to escape it may lack speed to do so, is not to be considered in battleship design.
Logically, the fastest battleships should belong to that country whose political situation requires it to maintain the most powerful navy. In this way it can always be sure of the battle which its strength causes it to desire.
As foreign battleships are now making 19 knots, I think 18 knots is enough for us. Let us make sure of heavy batteries and well trained crews, and then try to make up the difference in trial speed by assiduous care of the machinery.
If we look at the table to compare an 18 knot with a 19 knot Virginia, we see that the latter would have an advantage of over 500 tons in available weights for guns and armor. By doing away with the 6-inch battery, an 18 knot ship might be designed to carry four 12-inch guns in two turrets, four 8-inch turrets like the Indiana, two superposed 8-inch turrets like the Kentucky and eight 8-inch guns in broadside casemates, making a main battery of four 12-inch and 20 8-inch guns. If the difficulties in ammunition supply are not too great for solution, this battery would be the heaviest afloat, and to my mind it is a feature cheaply purchased by the loss of only a knot in speed.