Page:Popular Science Monthly Volume 91.djvu/699

 Popular Science Monthly

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��engine in order to produce that explosively- rapid combustion which makes the piston move up and down in its cylinder. And so mechanism is provided which enables the engine to inhale a measured quantity of air to be mixed with a measured quantity of fuel.

Now the air within a submarine is limited in quantity. When the ship is sub- merged, the crew must breathe as well as the engines. Moreover, there is the problem of disposing of the gases exhausted by the engine. They cannot be ejected into the sea carelessly. They would rise to the surface of the water in the form of bubbles and would inevitably betray the course taken by the submarine. Moreover, en- gines are very hot, and the living quarters in a submarine are at best none too com- fortable.

Because the air supply within a sub- marine is so limited and because of the very nature of the propelling engines, in- ventors of submarines have had to resort to the very awkward expedient of driving their craft under water by means of storage batteries. The batteries are heavy, cum- bersome, and not always safe; they must

��Periscopes Operating compartment Escape hatch

��be recharged at the surface — a noisy busi- ness which takes from six to eight hours and which imperils the safety of the craft for the time being. It is said that the newest German submarines can travel un- der water for nearly a hundred hours. That must mean a very sparing use of the' stored power. According to Lieutenant Hinkamp of our Navy, "the submarine of the present day can operate submerged at its maximum speed for about an hour. At about one-third of this maximum speed, she can operate practically twenty-four hours."

Is it not evident, as I maintain, that the submarine, mechanically speaking, is a very crude contrivance, something of which mechanical engineers should be ashamed rather than proud?

Needless to say the inconvenience and danger resulting from the necessity of using storage batteries for sub-surface propulsion have long been recognized. Inventors have made many efforts to do away with the storage battery entirely and to devise a way of using the regular internal combus- tion engines of the craft for under-water as well as for surface propulsion. Here, I wish to add my own contribution to the solution of the problem.

It is very evident that if the engines are

to be used for under-water propulsion

a large supply of air

must be stored in

Steering rudder

���Sufficient to Drive the Submarine under Water at High Speed and for Long Distances

��through the third coil, which is bathed by the hot exhaust Rases from the explosion engine. Still under pressure, but highly superheated, the oxygen passes into the expansion engine where it helps to drive the vessel and where it is expanded to a pressure equal to that which is required to force it into the explosion engine. In order that no visible wake may be left, the gases ex- hausted from the explosion engine are forced out through a sieve having many small holes. Thus the carbonic acid gas, of which the exhaust is largely composed, is finely

��subdivided so that it can be readily absorbed by the sea water. This absorption is aided by the propeller which thoroughly beats up the exhaust gases with large volumes of water.

If small cruising radius and quick action alone are required rather than economy, the expansion engine and the three coils through which the oxygen passes can all be cut out and the liquefied oxygen can be forced directly into the mixing tank and mingled with the proper amount of hot exhaust gases from the engine

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