Submarine and Anti-submarine

by Sir Henry John Newbolt

But what of the torpedo which has been fired? It is travelling towards its mark at a speed of between thirty-five and forty knots, if we suppose the range to be an ordinary one, under 1000 yards, and the torpedo to have been ‘run hot,’ i.e. driven by hot air instead of cold. The compressed air is heated mechanically inside the torpedo, in the act of passing from the air chamber to the machinery, and this increases both the speed and range. But it is not always convenient or possible to start the heating apparatus, and even when ‘run cold’ the fish will do thirty knots. This speed is amazing, but it is one of the least wonderful of the torpedo’s qualities. The steering of the machine is a double miracle. One device makes it take, after the first plunge, exactly the depth you desire, and another—a gyroscope fitted inside the rudder gear—keeps it straight on its course; or makes it, if you wish, turn in a circle and strike its prey, boomerang fashion. The head of the fish can also be fitted with cutters which will cut through any torpedo-netting that a ship can afford to carry. The only thing that no ingenuity can accomplish is to make a torpedo invisible during its run. The compressed air, when it has passed through the engine, must escape, and it comes to the surface in a continuous boiling line of bubbles. This is visible at a considerable distance; and though, when the track is sighted by the look-out, the torpedo itself is of course always well ahead of the nearest spot where the bubbles are seen rising, it is surprising how often ships do succeed in avoiding a direct shot. A prompt cry from the look-out, a steersman ready to put his helm over instantly, and the torpedo goes bubbling past, a few feet ahead or astern, or comes in on a tangent and runs harmlessly along the ship’s side without exploding. Then away it goes across the open sea, until the compressed air is exhausted, the engine stops, and the mechanical sinker sends it to the ocean bed, which must be fairly strewn with dead torpedoes by this time; for as we know, to our advantage, the proportion of misses to hits is very large in the U-boat’s record.

Now that you have seen the weapon—and can at any rate imagine the handling of it—you are naturally keen to sight the game, and realise the conditions of a good shot. You go back to the central compartment, where the Commander is ready to show you a ship through the periscope. Not, of course, an enemy ship—in this war, if you want a shot at an enemy ship, you must go into his own waters—into the Bight or the Baltic—to find him; and even there he is probably tucked up very tight in his berth, with chained barges and heavy nets all round him, and mines all up the approach. But there are plenty of our own ships out every day—sweeping, cruising, trading; and transporting men, food, mails, and munitions. And what you see will help you to understand why the Germans have spent so many torpedoes, and sunk so comparatively small a proportion of our enormous tonnage.

The boat is now less deep in the water; the gauges mark 15 feet, and you are told that the top of the periscope is therefore some two feet above the surface. The shaft of it is round, like a large vertical piston; but at the bottom it ends in a flattened box, with a hand-grip projecting on each side. You take hold of the grips and look into the box. Nothing is visible but an expanse of water, with a coast-line of low hills beyond it—all in miniature. The Commander presses the back of your left hand on the grip, and you move round slowly as the periscope revolves. The coast-line goes out of the picture, the sea lies open to the horizon, and upon it appears a line of odd-looking spots. They are moving; for the nearest one, which was narrow a moment ago, is now three or four times as broad, and is in a different place in the line.

The line, you are told, is not a line at all, but a convoy, in fairly regular formation. The nearest spot is a destroyer, zigzagging on the flank; the others are ships which have been so effectively ‘dazzled’ that their shapes are unrecognisable. You carry on, in hope of something nearer, and suddenly a much larger object comes into the field of vision. A ship, of course, though it does not look like any ship you have ever seen; and you are asked to guess its distance and direction. You are bewildered at first; for as you were moving the lens rapidly to starboard, the vessel came in rapidly to port, and as her dazzle-paint makes her stern indistinguishable from her bows, you continue to think she is steaming in that direction. After a more careful observation, this mistake is corrected. She is crossing us from port to starboard. But at what angle? This is vitally important, for the possibility of getting in a successful shot would depend entirely upon the answer. We are ourselves heading about due north: she is crossing to the east: if her course is south of east, she is coming nearer to us, and our torpedo would strike her before the beam—the most favourable chance. If, on the contrary, her course is north of east she is going away, and the torpedo would have a poor chance of hitting her abaft the beam. In fact, it would not be worth while to risk losing so costly a shot. A torpedo at present prices is worth not far short of £2000, and we only carry two for each tube.

You look long and hard at this dazzle-ship. She doesn’t give you any sensation of being dazzled; but she is, in some queer way, all wrong—her proportions are wrong, she is somehow not herself, not what she ought to be. If you fix your attention on one end of her, she seems to point one way—if you look away at her other end, she is doing something different. You can’t see the height of her funnels clearly, or their relative position. But, with care, you decide that she is coming about south-east and will be therefore your bird in two minutes’ time. The Commander is interested. He takes a look himself, laughs, and puts you back at the eye-piece. You hold on in hope that he may, after all, be wrong; but the bird ends by getting well away to the north-east. Your error covered just ninety degrees, and the camouflage had beaten you completely. You begin to think that the ingenuity at command of the nation has been underestimated. But this ship is nothing of a dazzle, the Commander tells you—he can show you one whose cut-water seems always to be moving at a right angle to her stern!

‘Does not look like any ship you have ever seen.’

He adds that he knew all about that cruiser, and she knew all about him. Otherwise he would not have shown even his periscope; and if he had, she would have had a shell into him by now, and a depth-charge to follow. A depth-charge is perhaps the most formidable weapon against which the submarine has to be on guard. It is a bomb, with a detonator which can be set to explode when it reaches any given depth. A small one would need to hit the mark full, or be very close to it, in order to get a satisfactory result; but the newer and larger ones will seriously damage a submarine within an area of forty yards. The charge is either dropped over the stern of the pursuing vessel, when she is thought to be just over or just ahead of the enemy; or it is fired out of a small and handy short-range howitzer—a kind of lob-shot, a number of which can be made by several patrol boats acting together, so as to cover a larger area with much less risk of embarrassing each other. Even if the submarine is not destroyed outright, the chances are in such a case that she will be so damaged as to be forced to the surface or to the bottom, and then the end is certain. A bad leak would bring her up—an injury to her tanks or rudders might drive her down.

You are uncomfortably reminded once more of that inherited dislike of death by suffocation. If a submarine cannot rise to the surface, you ask, is there no possible means of escape? The answer is that it may be possible, with great difficulty, to get out of the boat; but there is very little chance that you would survive. The lungs are not fitted to bear so great and sudden a change of pressure as that felt in passing from the boat to the water, and from the deep water to the surface. You are perhaps surprised; but the pressure of sea-water at 160 feet is equal to five atmospheres, or about 75 lbs. to the square inch. To pass safely through this to the ordinary surface atmosphere would need a long and gradual process, and not a sudden rise of a few seconds. A very brave attempt was made on one occasion, when a British submarine had gone to the bottom during her trials, and could not be got up by any effort of her crew. The agony of the situation was intensified by the fact that help was close at hand, if only the alarm could be given, and the whereabouts of the submarine communicated to the rescuers. The officers of the sunken boat were, of course, perfectly aware of the danger from sudden change of pressure; but one of them volunteered to go to the surface, alive or dead, and carry a message on the chance of attracting some ship’s attention. To lessen the risk as far as possible, it was arranged that he should go up into the conning-tower, and that the hatch should then be closed beneath him and the water gradually admitted. As it flowed slowly in, and mounted round him, the air in the top of the conning-tower would diminish in extent but increase in pressure. When it reached his neck, the internal pressure would be nearly equal to the external. He would be able to open the top, possibly to make his escape, and conceivably to reach the surface without his lungs being fatally injured. If he failed, he would at any rate have given his life for the chance of saving his comrades.

The Commander accompanied him into the conning-tower, meaning, it is said, to return into the ship himself when he had seen to all the arrangements. But when the water was admitted, the two of them were shot out together, and as it happened it was the volunteer who was killed, by striking against the superstructure, while the Commander came up alive. In no long time—though it must have seemed unendurably long to those below, waiting in complete uncertainty—the rescuers were informed, found the submarine, and got a hawser under her stern. They raised her high enough out of the water, vertically, to open a hatch and save the crew. Then the hawser gave, and the boat went down again.