Page:Popular Science Monthly Volume 91.djvu/902

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Protecting Battleships with Compressed Air

Should a vessel be torpedoed the inrush of water will be stopped by outrushing air under pressure

��UNCLE SAM'S ships have been turned any event the pressure of the air in the

into giant diving bells or caissons nearest surrounding intact compartments

to help protect them from torpedo acts equally in all directions and is liable

attack. It sounds impossible, but it is not; to make the bulkheads and decks leak,

for it is merely adaptation of the principle For this reason air at a lower pressure is

��of the air lock. This has been used for many years in sinking underwater foundations or driving tunnels under rivers and even in ship salvage work. The hulls of the ships have simply been divided into a large number of compartments to be filled with compressed air.

Should one or more of these compartments or chambers be shattered by the explosion of a tor- pedo or mine, the ad- jacent compartments are filled with compressed air until the pressure of the air counterbalances that of the water in the dam- aged section. When this occurs, no more water can flow into the vessel and she may be towed into port or proceed under her own steam if her engines have not been damaged.

Almost the same con- ditions hold true in or- dinary household work when an empty tumbler is plunged bottom upward into a dish-pan of water. The water enters just so far, until the air trapped in the glass is com- pressed to a point where its pressure equals that of the water. Then no more will enter.

As shown in the accompanying illustra- tion, the hull of the ship is divided into a great number of compartments. Should one of these be punctured by any means, the ones next it are immediately filled with compressed air until the water pressure is equalized and no more can flow in. The compressed air may or may not come into contact with the water in the damaged compartment, according to whether one or more than one chamber is punctured. In

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The wake of the torpedo. It is the only warning which the threatened vessel usually has

��pumped into the adjacent compartments, the pres- sure diminishing as the distance of the chambers from the damaged area increases. In this man- ner, the difference in the pressures in the adjoining compartments is only a few pounds and the bulk- heads and decks are well able to withstand it with- out leaking.

The use of this system has occasioned very little change in the design of the vessels, for battle- ships always have been divided into many cellu- lar divisions for restrain- ing the inflow of water through damage by col- lision. Again, means for pumping the compressed air into the compart- ments was already | in place in the form of pipes to pump fresh air into and exhaust foul air from the chambers.

Compressed air is also a common commodity on battleships, being used to run the refrigerat- ing machines, to fire torpedoes as well as charge them and to remove the hot gases from the gun barrels after firing. It was therefore only necessary to provide suitable means for connecting the compressed air supply with the compartment pipes. This did not of course change the design of the inner hull or appreciably increase its weight. The system, the invention of William Wallace Wotherspoon, a New York City engineer, was first installed on the armored cruiser North Carolina. All of our recent battleships have the system, so that our sailors crossing the seas or working in the war zone have a chance against torpedoes.

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