The Journal of Submarine Commander von Forstner

by Freiherr von Georg-Günther Forstner

SUBMERSION AND TORPEDO FIRE

A new passenger, for the first time in a submarine, has often professed to be unaware that he was fathoms deep under water and has been quite unconscious that the boat had been diving. Of course his astonishment indicates that he was not in the compartment where these maneuvers take place, for it is in the commander's turret that the whole apparatus is centralized for submersion, for steering to the right depth, and also for emersion. At this juncture every man must be at his post, and each one of the thirty members of the crew must feel individually responsible for the safety of the whole in the difficult and rapid maneuver of plunging, for the slightest mistake may endanger the security of the boat.

The central control, situated in the commander's turret, is in reality the brain of the boat. When the alarm signal is heard to change the course from surface navigation to subsurface navigation, several previously designated members of the crew take their post of duty in the commander's turret. The commander, himself, is on duty during the whole of the expedition in time of war, and he seldom gets a chance for rest in his tiny little cabin. Day and night, if there is the slightest suspicion of the approach of the enemy, he watches on the exposed bridge on the top of the turret; for a few seconds' delay in submerging might forfeit the taking of a much coveted prize. So he learns to do without sleep, or to catch a few brief seconds of repose by lying down in his wet clothes, and he is at once ready to respond to the alarm signal of the officer of the watch.

In one bound he is once more surveying the horizon through the periscope, or mounts to the bridge to determine with his powerful field glass whether friend or foe is in sight. His observations must be taken in the space of a few seconds, for the enemy is also constantly on the lookout, and continual practice enables the sailor in the crow's nest to detect the slender stem of a periscope, although the hull of the boat is scarcely visible on the face of the waters.

The commander must come to a prompt decision as soon as he locates the adversary's exact position. Not only may a retarded submersion spoil our plan of attack, but we are exposed to being rammed by a rapidly advancing steamer; our haste must be all the greater if the conditions of visibility are impaired, as is often the case on the high seas, for it takes time for the U-boat to submerge completely, and during this process it is helplessly exposed to the fire of long distance guns.

Calmly, but with great decision, the commander gives the general orders to submerge. The internal combustion engines, the oil motors which, during surface navigation are used to accelerate the speed of the boat, are immediately disconnected, as they consume too much air underseas, and electric motors are now quickly attached and set in motion. They are supplied by a large storage battery, which consumes no air and forms the motive power during subsurface navigation. Of course electricity might be employed above water, but it uses up much current which is far more expensive than oil, and would be wasted too rapidly if not economized with care.

It would be convenient to employ the same oil motor for underseas navigation, but such a machine has not yet been constructed, although various futile attempts of this kind have been made. With only one system of propulsion we should gain much coveted space and a more evenly distributed weight; within the same dimensions new weapons of attack could be inserted, and also effective weapons of defense. The inventor of such a device would earn a large reward. Let him who wants it, try for it!

Quickly, with deft hands, the outboard connections, which served as exhausts for the oil motors, must be closed in such a way as to resist at once the high water pressure. It is well known that for every ten meters under water we oppose the pressure of one atmosphere—one kilogram to the square centimeter—and we must be prepared to dive to far greater depths.

When all these openings have been carefully closed and fastened, then begins the maneuver of submersion. The sea water is admitted into big open tanks. Powerful suction engines, in the central control of the boat, draw out the air from these tanks so as to increase the rapid inrush of the water. The chief engineer notifies the captain as soon as the tanks are sufficiently filled and an even weight is established so as to steer the boat to the proper depth for attack. Notwithstanding the noise of the machinery, large, wide-open speaking tubes facilitate the delivery of orders between the commander's turret and the Central, and now is the moment the commander gives the order to submerge.

All this may sound very simple and yet there are a great many things to consider. In the same manner in which an airplane is carefully balanced before taking wing into the high regions of the sky, a submarine must be accurately weighed and measured before it descends into the watery depths of the ocean. The briny water of the North Sea weighs far more than the less salty water of the Baltic Sea, whose western basin is composed of practically fresh water. A boat floats higher in the heavily salted waters of the North Sea and lies deeper and plunges farther down in the waters of the Baltic. The same U-boat, therefore, must take into its tanks a greater quantity of water ballast in the North Sea, to be properly weighted, than when diving into fresher waters. Even with small submarines of 400 tons displacement, there is the enormous difference of 10 tons between 1.025 specific weight in the intake of North Sea water and 1.000 specific weight of fresh water. On the other hand, if too much water is admitted into the tanks, the submarine may plunge with great velocity deeper and deeper beyond its appointed depth, and in such a case it might even happen that the hull of the boat could not withstand the overpowering pressure and would be crushed beneath the mass of water. And yet again if too small a quantity of water ballast is admitted into the tanks, the boat may not sink sufficiently below the surface, and thus we could not obtain an invisible attack which is positively necessary for our success.