Popular Science Monthly
��Vol. 89 No. 3
��239 Fourth Ave., New York
��Torpedoing a Submarine from an
��BECAUSE an airman flying above the water can sight an underwater craft and detect its approximate depth with the naked eye, inventors ha\e de- vised a number of bomb-dropping con- trivances in an endeavor to make the most of this strategic advantage and place the submarine at the mercy of the aeroplane. One of the most recent of these devices is an aerial torpedo or bomb containing high explosive which when dropped from the aeroplane makes a rapid and straight descent Ijeneath the water and explodes at the proper depth and [)roximity to wreck a sulimarine.
The bomb consists of a shell filled with high explosive and into its closed end is fixed a detonator which consists of a tube containing a layer of metallic sodium, a layer of gun cotton and a layer of ordinary fulminate. Attached to the shell is a parachute, which is nothing but a dished circular plate. This acts as a guide in the descent of the bomb from the aeroplane to the water and also regulates the speed of the bomb once it is under water, allowing it to sink slowly.
The cover of the bomb as well as the cap of the detonator-tube are perforated. When the bomb has sunk to a certain distance, water flowing in through these perforations ignites the sodium (a prop- erty of sodium), which fires the gun cotton, which discharges the fulminate, which sets otT the bomb. These different stages leading up to the actual explosion occur nearly simultaneously, but should they fail — that is, should the unforeseen happen and the sodium not ignite, an electrical igniting mechanism is provided which will discharge the fulminate.
��\Miliin the shell there is a dry battery connected to a contact point and to one entl of a platinum glow wire embedded in the fulminate. The other end of the glow wire is connected to an insulating lever carrying a contact point. This lever member is a closed hollow tube containing a little mercury, which, flow- ing to the lower end, tends to keep the lever down. A tube in the perforated cover contains a bucket filled with a dry sponge.
When once the bomb has struck the water and the sponge has sufficiently absorbed it, its weight bearing on the end of the lever member raises this lever into contact with the terminal, thus completing the circuit and discharging the fulminate.
There are sexeral very obvious objec- tions to a bomb of the type described. It is ver\- difficult to hit an object on the ground when the aeroplane is very high. Indeed, no satisfactory' instru- ment has thus far been invented to drop bombs from great heights with anything like the precision that marks the firing of projectiles from great guns. If the aeroplane is to destroy a submarine in the manner proposed, the bomb-dropper must be very near its target — so near that it would itself be in danger from gun fire.
Some of the difficulties of dropping bombs accurately spring from the fact that an aeroplane moves through the air at a rate of at least forty-five miles an hour. Allowance must be made not only for that forward movement, but also tor the movement r)f the submarine as well as for the wind. A hit would therefore be almost a matter of luck.