Page:Popular Science Monthly Volume 92.djvu/358

 Would She Be Crushed by the Sea?

How the Navy finds out if submarines may be submerged with safety to great depths

Bv Robert G. Skerrett

��IT has recently been said that many of Germany's submarines have been car- ried to the bottom by reason of in- herent weaknesses — structural faults, in brief. This means that the hastily built U-boats have sprung a leak and foundered simply because the defects were not dis- covered before sending the craft out upon active service.

The Italians shrewdly anticipated the results of wartime pressure in turning out in haste a large number of under-water torpedo boats; and Major Cesare Lau- renti cleverly designed a testing dock which would make it possible to subject a submarine to the physical stresses of sub- mergence at any practicable depth without risking the boat the while in deep water. That is to say, the submersible could be tested in harbor, right at the building yard, where her constructors could make sure that she was absolutely sound in hull. The United States Navy also uses the Laurenti dock to determine thp fitness of its submarines for sea.

How can this be done ? The hulls of these vessels must be sturdy enough and tight enough to withstand the searching pressure of the sea -iOO feet down below the surace. Laurenti's novel dock consists mainly of a long steel tube which is capable of resisting a pressure from within corre- sponding to a crushing force at any prescrib- ed submergence; only the dock always remains at the surface. One end of this tube is perma- nently sealed, and the other can be closed by a great, gloi)ular caisson or gate. By swinging when the submarine

this gate aside, {jreat globular door

���when the dock is in proper condition, a submarine can be floated into the tube, settled upon keel blocks and otherwise held from shifting when the gate is sealed. The cylinder is completely filled with water. The submarine is then subjected to external pressure just as she would be if lowered deep into the sea. But there is this difference; her crew are inside of her and stationed where they can watch for leaks and observe certain instruments that show how much the hull yields to the exterior water pressure, and whether or not the structure returns to its original lines when this pressure is relieved. The testing pressure is gradually raised by means of powerful pumps on the dock. They try to force more water into the already filled cylinder, and thus the sub- marine is subjected to a crushing force which can be raised to correspond with that at any assumed depth.

During the test, the observers in the submarine are in telephonic communica- tion with the people in charge of the pumping plant, and should anything go wrong or a grave leak develop, the pres- sure can be lowered instantly and the great tube drained in a few minutes. Thus, while imitating the conditions of a deep submergence there are none of the

dangers that might be met if the boat were out at sea.

In the last few years, un- der- water tori)edo boats have bern modi- fied in order to meet changing military needs. The Laurenti dock makes it possible to try them out be- is well inside, the ^O^e gomg into

is tightly closed actual servlce.

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