Figure 10-2.-Depth-setting dial.into the detonator. The booster, already in position, thenfires and, in turn, sets off the entire load of TNT.These two bellows—operated by hydrostaticpressure—serve two purposes. First, they permit thedepth charge to fire at the proper depth; second, theymake the charge safe to handle and carry. If you shouldaccidentally knock the safety fork and the valve inletcover off on deck, nothing would happen. Even if thedetonator should go off while you were handling thecharge, the main charge would not fire unless the boosterwas in the extended position.Guiding TorpedoesTo keep a torpedo on course toward its target is ajob. Maintaining the proper compass course with agyroscope is only part of the problem. The torpedo musttravel at the proper depth so that it will neither pass underthe target ship nor hop out of the water on the way.As figure 10-3 shows, the torpedo contains anair-filled chamber sealed with a thin, flexible metalplate, or diaphragm. This diaphragm can bend upwardor downward against the spring. You determine thespring tension by setting the depth-adjusting knob.Suppose the torpedo starts to dive below theselected depth. The water, which enters the torpedo andsurrounds the chamber, exerts an increased pressure onthe diaphragm and causes it to bend down. If you followthe lever system, youpush forward. Noticecan see that the pendulum willthat a valve rod connects theFigure 10-3.-Inside a torpedo.pendulum to the piston of the depth engine. As the pistonmoves to the left, low-pressure air from the torpedo’s airsupply enters the depth engine to the right of the pistonand pushes it to the left. You must use a depth enginebecause the diaphragm is not strong enough to move therudders.The piston of the depth engine connects to thehorizontal rudders as shown. When the piston moves tothe left, the rudder turns upward and the torpedo beginsto rise to the proper depth. If the nose goes up, thependulum swings backward and keeps the rudder fromelevating the torpedo too rapidly. As long as the torpedoruns at the selected depth, the pressure on the chamberremains constant and the rudders do not change fromtheir horizontal position.DivingNavy divers have a practical, first-hand knowledgeof hydrostatic pressure. Think what happens to diverswho go down 100 feet to work on a salvage job. Thepressure on them at that depth is 8,524 pounds persquare foot! Something must be done about that, or theywould be flatter than a pancake.To counterbalance this external pressure, a diverwears a rubber suit. A shipboard compressor then pumpspressurized air into the suit, which inflates it andprovides oxygen to the diver’s body as well. The oxygenenters the diver’s lungs and bloodstream, which carriesit to every part of the body. In that way the diver’sinternal pressure is equal to the hydrostatic pressure.As the diver goes deeper, the air pressure increasesto meet that of the water. In coming up, the pressure onthe air is gradually reduced. If brought up too rapidly,the diver gets the “bends.” That is, the air that wasdissolved in the blood begins to come out of solution10-3
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