Shooting the Torpedo.—Now let’s see just what happens from the moment an enemy ship is sighted up to the time the torpedo hits it and explodes.
An up-to-date torpedo makes about 40 knots, and it will travel about six miles before its compressed air is used up. But it cannot be aimed and shot with certainty at a distance of over half a mile. So when an enemy ship is sighted, the submarine creeps up upon her, with nothing but her periscope out of the water, until she is within accurate shooting range.
In the meantime the speed of the enemy ship has been calculated, the depth at which the torpedo must travel to strike the ship below the water-line has been determined, and the angle, or course, the torpedo must take to hit the ship is figured out.
Due allowance must be made for the speed of the ship and the speed of the torpedo to the end that the distance both will travel in a given time may be known. Of course, if the ship is speeding along and the torpedo is shot point-blank at her it will pass a good many yards astern of her.
This operation is very much like that of rabbit hunting, in which you do not fire directly at the running rabbit, but aim several feet ahead of him, and he simply runs into the bullet or shot. So it’s all his fault if he gets killed. Just so with the ship and the torpedo; for instead of the torpedo running into the ship, the ship runs into the torpedo, and so if the ship sinks it isn’t the fault of the torpedo—or at least that is the way the German captain of a U-boat looks at it.
Before the torpedo is loaded into the torpedo tube the safety pin is taken out of the firing pin and the butterfly-nut is loosened so that it will unscrew easily. The torpedo is then slipped into the tube and the breach-block of the tube is closed. The compressed air is now turned on at the torpedo air tank; when the air rushes into the torpedo tube behind the torpedo, but the latter is kept from being forced out by a lock.
The Course of the Torpedo.—Next the captain sights his ship and finds its speed and its distance from his own craft. To direct the torpedo so that it will hit her target fairly, an instrument called a torpedo director is used. It is shown in [Fig. 44], and this picture also shows how the torpedo and the ship come together.