Page:Popular Science Monthly Volume 91.djvu/396

 The Mother of the Submarine

��As a complete floating naval base, the submarine mother-ship is indis- pensable in our submarine program because of our two long coast lines

��\S everyone knows, — and as Germany /-\ long ago learned to her sorrow, — the Strait of Dover has been planted and re-planted with British mines until it would be sheer suicide for a German submarine to attempt to pass through. In order to attack England's shipping, German submarines have therefore been compelled to travel all around the British Isles. In making this tedious detour, a great tax is laid upon the submarine's com- paratively delicate machinery. And since this journey must be made under the water most of the way, an even greater strain falls upon the crew. If the submarine and its crew ever get back, both will be in dire need of repairs.

Here is where the mother-ship justifies her name. On returning to its assigned harbor and signaling by wireless to its parent-ship, the submarine is immediately taken in between the ship's steel hulls and is finally sheltered in the tubular compart- ment amidships. The compartment is water-sealed and huge pumps on the mother-ship are started forcing the water out — thus converting the compartment, in effect, into a wonderful floating drydock. The submarine's crew are received by the mother-ship and are accommodated in extra cabins especially la'd aside for them. Here they can sleep on real beds and take their well-earned rest.

Meanwhile, the lathes and forges are busy fashioning new parts and the duplicate submarine members carried by the mother- ship are mounted in place of those worn out or damaged. The duplicate mechan- isms are stored mostly on the decks. The heavy lathes, on the other hand, are mostly below; not exactly below deck, however, but more correctly, in between the two walls of steel which together make up each of the twin hulls. Occupying the re- maining space between these steel walls are ballast and fuel oil tanks, torpedo and other stores. In here also, and in the hull at the front of the tubular docking compartment — which at this section looks like the hull of any ordinary ship, are the marine oil engines for driving- the ship. The cast-steel propellers with which these connect project backward, one from each of the twin hulls.

��In a few days' time, the submarine is completely overhauled, and her food and fuel supplies are replenished. Those of her original crew who are unable to stand the strain of the next journey are relieved by trained men on the mother-ship. When the new submarine crew have taken their places, the docking compartment is flooded, the ballast tanks trim the ship further, and the submarine takes to the sea again with renewed strength. When we consider that one ship can mother a flotilla of six sub- marines, scheduling four on active duty, one in reserve and one in repair, the stra- tegic importance of this type of vessel in the present war is evident. Without put- ting back for new supplies, and without touching her own supplies, she can re- juvenate a complete flotilla four times!

After a submarine has been on active duty a number of months, she is likely to develop a weakened hull, a fault which cannot be detected by ordinary methods. Here again the mother-ship is of prime importance. She is specially equipped to convert her tubular compartment into a testing dock. Her powerful pumps will force the water into the testing dock until the conditions are simulated that exist at the dizzy depth of two hundred feet below the water's surface — a submarine rarely dives down more than fifty! The testing crew within the submarine are in constant communication by telephone with the men at the pumps. If any weakness has developed, leaks will soon be noticeable, and the water pressure can be relieved before further damage results. These leaks, and whatever other faults are found, are noted and subsequently repaired.

The last, but not the least important function of the parent-ship, is that of a salvage boat. If a submarine sinks within reach of divers, a mother-ship will be able to save her, provided she can be suffi- ciently protected from the enemy by friendly warships or by her own quick-firing guns. Mother-ships have a cruising radius of four thousand miles and they can speed towards the place of disaster at the rate of ten knots. Expert divers are ready to wrap a cable around the sunken submarine, and powerful cranes are made ready to haul it up.

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