Submarine and Anti-submarine

by Sir Henry John Newbolt

The feelings of the average landsman, when he sets foot for the first time in a submarine, are a strong mixture of curiosity and apprehension. The curiosity is uppermost—the experience before you is much more novel than, for example, that of a first trip in an aeroplane. From a mountain or tower, a great wheel or a balloon, you have seen the bird’s-eye view of the earth and felt the sensation of hanging over the aerial abyss. But even the fascinating pages of Jules Verne have not told you all that you will feel in a submarine, and nothing but physical experience can do so. You are eager to see the working of new mechanical devices in a wholly strange element, and to learn the use of a new weapon in a wholly strange kind of war. But with this eagerness, there is an underlying sense of uneasiness, a feeling that you are putting yourself into a position where you are as helpless as a mouse in a patent trap. The cause of this is not fear of war risks, for it is equally strong in harbour, or in time of peace. It is probably connected with the common dread of suffocation, which may be an instinct inherited from ages of primitive life in the open. They will tell you, in the submarine service, that it is a mere habit of mind and very soon forgotten. There is even a story of an officer who, on coming ashore from a year’s work in an E-boat, refused to travel in the Tube railway, because it looked so dangerous. He preferred the risks he was used to, and so do most of us.

You stand, then, at the foot of the narrow iron ladder down which you have come from the upper air, you gag your inherited instinct, and let your curiosity loose. Before the boat dives, there is time for a good deal to be taken in. The interior seems large beyond expectation. This is partly an illusion, produced by the vista of the compartments, fore and aft of the central control where you are standing. The bulkhead doors being all open at this moment, you can see into the engine and motor rooms towards the stern, and forward through the battery compartment to the bow torpedo-tubes. The number of men seems large too, and they are all busy; but you note that every part of them is more active than their feet—there is very little coming and going. In the control, close to you, are the captain, a lieutenant, a steersman, and seven or eight other men for working the ballast tanks, air valves, electrical apparatus, and hydroplanes. The last two of them have just come down from the deck—the hatches are closed—engines have already been running for some minutes, though the order escaped your observation.

You are invited ‘to see her dive.’ You go up to the forward conning-tower scuttle and flatten your face against the thick glass. An order is given. You hear the hissing of air, as the ballast tanks are filled. You expect to see the forward part of the boat dip down into the water in which she is heaving. Instead of that, it is apparently the sea which lifts itself up, moves along the deck, and seems to be coming in a huge slow wave over your scuttle. The light of day gives place to a green twilight, full of small bubbles. Mentally you feel a slight chill; but physically, a warm and sticky sensation. As there is nothing more to be seen out of window, you return to your instructor. He explains to you that the ship is now running on her motors, and that her speed is therefore low—not nearly enough to overhaul a vessel or convoy of any power. On the surface, with her other engines, she could far more than double the pace; and even with the motors, she could do a spurt for a short time—but spurts are very expensive; for they use up the battery power with ruinous rapidity, and then a return to the surface will be necessary, whether safe or not.

At this point it may strike you suddenly that you are now under water—you begin to wonder how deep you are, and why you have not perceived any change in the boat’s position. The answer is that the depth marked on the gauges is only twenty feet, and the angle of descent was therefore very slight—much too slight to be perceptible in the short length of a single compartment. The depth of twenty feet is now being maintained with surprising steadiness; the explanation is that two entirely separate forces are at work. First, there are the horizontal rudders or hydroplanes, fitted outside the vessel both fore and aft, by which she can be forced down, provided she has sufficient way on, in much the same fashion as an ordinary vertical rudder forces a ship to one side or the other. But this is only the diving apparatus; to keep her down, there is her water ballast—the water which was taken into her main ballast tanks, when the order to submerge was given. These tanks contain a sufficient weight of water to counteract the normal buoyancy of the boat, by which she would naturally float upon the surface. When they are emptied, she will neither sink nor rise of her own motion—she will lie or run at whatever depth she is placed, by her hydroplanes or otherwise.

These, you will have noticed, were called the ‘main’ ballast tanks—there would seem then to be others. There are, and several kinds of them. First, there is an auxiliary ballast tank, which has a peculiar use of its own. A submarine must be able to float or submerge in fresh water as well as at sea; for her base or harbour will often be in the mouth of a river, or she may have to navigate a river, a canal, or a lake. It is a point that would not probably have occurred to you, but the difference between the density of fresh and salt water is sufficiently great to make a real difficulty here. Everyone knows that it is less easy to float in fresh water, and less easy to sink in salt. For practical purposes, a submerged boat is less buoyant in fresh water by 26 tons in 1000, and vice versa; so that when a submarine of 1000 tons leaves a river for the sea, she must take an extra 26 tons of ballast to keep her down, and when she comes home again she must get rid of 26 tons, or she will sink so much deeper in the fresh water. For this purpose she has a special tank of the right size, proportioned to her tonnage; and it is placed in the middle of the ship, in order that it may not interfere with her trim when it is filled or emptied.

That last remark will put you in mind that, in any kind of navigation, the trim of the boat is a delicate and important matter. Even in very large and heavy ships you may be able, by shifting guns or cargo, to slip off a shoal, or right a leaking vessel after a collision. In a tickle boat like a submarine, it is necessary to have some means of trimming the vessel, fore or aft, at any moment, and especially when about to dive, or when caught by some under-water obstruction. Tanks are therefore fitted for this purpose at each end of the boat. They are comparatively small, because the effect required is in ordinary circumstances very limited, and in a desperate emergency they may need to be supplemented by rushing the crew fore or aft, as living ballast. An example of this will be found in a later chapter.

You may now feel that you have heard enough of tanks; but your instructor will insist on showing you a whole additional series. He will make a point of your recognising that a submarine, when submerged, is in reality hanging in the water as a balloon hangs in the air, and for every loss of weight she must be instantaneously compensated, or she will begin to rise. What loss of weight can she suffer while actually under water? It is not perhaps very hard to guess. There is, first of all, the consumption of oil by the engines; secondly, the consumption of food and fresh water by the crew; and thirdly, the departure from time to time of torpedoes. Also, when on the surface, there may be gun ammunition fired away, or other things heaved overboard, and allowance must be made for this when the boat goes down again. The modern submarine is prepared to keep her balance under all such circumstances. She has compensating tanks, and they are placed as near as possible to the oil-tank, fresh-water tank, or torpedo-tube, for whose diminished weight they are to compensate.

You are probably more interested in the torpedo-tubes than in the oil-tanks. It is time then to go forward. You pass through the battery compartment, where the officers’ quarters are, and are shown (under the floor) the accumulators, ranged like the honey sections in the frames of a beehive, and very carefully covered over with flexible waterproof covering as well as with close-jointed planking. What would happen if water did find its way down to the batteries? An instant discharge of chlorine gas, blinding and suffocating. What would you do then? Come to the surface at all costs—and lucky if you are in time! The Germans know all about that—and not long ago one of our own boats was only saved by the good goal-keeping of a lieutenant, who caught up a lid of some sort, and stood by the leak, neatly fending off the water spurt from the door of the battery compartment.

Now you are in the forward torpedo compartment, and there are the tubes. I need not say anything about their size or number—you will realise at a glance that when a couple are loosed off at once, a good deal of weight goes out of the ship. The ordinary 18-inch fish is 17 feet long, and takes some handling. The explosive alone in her war-head weighs as much as a big man, say 12½ stone, and a 21-inch fish carries twice as much as that, packed in some four feet of her length. Behind that comes the air chamber—another ten feet—with the compressed air to drive the engine, which is in her stern. The air is stored at a pressure of over 2000 lbs. to the square inch; so the steel walls of the chamber must be thick, and this makes another heavy item. Lastly, there is the engine-box with its four-cylinder engine, two propellers, gyroscope and steering gear. Altogether, an 18-inch fish will weigh nearly three-quarters of a ton, and a 21-inch over 2000 lbs., so that the amount of compensation needed when you fire, is considerable.

To see how it is done, we will imagine ourselves firing this starboard tube. The torpedo is got ready, and special care is taken to make sure that the firing-pin in her nose is not forgotten. Cases have been known in which a ship has been hit full by a torpedo which did not explode—just as a good many Zeppelin bombs were found in London, after the early raids, with the detonating pin not drawn. The fish is now ready to come alive, and is slid into the tube. The door is shut behind it, and the water-tight outer door, at the other end of the tube, is now ready to be opened by powerful levers. But the immediate result of this opening would be an inrush of sea-water which would weigh the boat’s head down; for though the fish’s belly fits the tube pretty closely, there is a good deal of empty space where it tapers towards the nose and tail. Here comes in the tank system. When the tube is loaded, this empty space is filled by water from within the ship, so that no change of weight occurs when you open the outer door. But when the firing-button has been pushed, and the torpedo has been shot out by an air-charge behind it there is no possibility of preventing the whole tube from filling with water, and this water must be got rid of before the tube can be reloaded. To do this, you first close the outer door again; then you have to deal with the tubeful of water. A good part of it is what the ship herself supplied to fill the space round the torpedo; and this must be pumped back into the special tank it came from. The remainder is the sea-water which rushed in, to take the place left empty by the departing torpedo: and this must be pumped into another special tank to prevent the ship feeling the loss of the torpedo’s weight. When you get a fresh supply of torpedoes, these special compensating tanks (which are really a kind of dummy torpedoes) will be emptied out, one for each new torpedo. Meantime, you have now got the tube empty, and can open the inner door and reload.