MAKING THE SUBMARINE DEADLIER
IT would naturally be supposed that a submarine carrying eight or more
torpedoes is about as destructive an engine as human ingenuity could
devise; but not so, for there are other _munitions_ of warfare with
which it is equipped that make it even deadlier.
Now, the word _munitions_ means war materials of every kind—except, of
course, men and money; but on a submarine the munitions are limited
to (1) the _automobile torpedo_, which we have described in the last
chapter; (2) _rapid-fire machine guns_, and (3) _submarine mines_.
In the present war Germany has undertaken the gigantic task of sinking
all the merchantmen, not only of the Allies but of the neutral
countries as well, and it is this U-boat policy which has brought her
into a state of war with nearly every civilized country on the face of
the earth.
As the torpedo is such a costly weapon, it would not do to waste it on
sinking any but the largest ships, or those carrying valuable cargoes;
but the same policy of Germany, which is to starve out the Allies, also
calls for sinking the smaller craft, such as trawlers and unarmed
merchantmen, and this is done by means of _rapid-fire machine guns_.
These guns are mounted fore and aft on the deck of the submarine, and
they are used to bring down small ships and also to enable the undersea
craft to defend herself against _submarine chasers_, airplanes, or
occasionally when she is surprised by a destroyer or other armed ship
which may get within firing range and attack her before she has time to
dive.
The submarine mine is as old as, or older than, the submarine boat
itself; and it was probably the idea of fixing a bomb onto or planting
a mine under a ship that led to the actual building of the first
underwater craft.
The mine is not, however, an explosive destroyer which is used by
the submarine boat; for she could never get close enough to an enemy
ship in these days of electric eyes and ears to make use of one. What
the submarine does do is to play the peaceful rôle of planting the
mines—not with the idea of making two grow where only one grew before
but of making one ship less where there was one ship more, and this is
done by blowing up the enemy ships which may chance to pass over them.
=Arming the Submarine with Guns.=—From what has been said above, you
will see that by the use of rapid-fire guns poor prizes can be easily
and cheaply sunk; further, a small craft always makes a bad target for
a torpedo and thus the odds of making a miss and losing a torpedo are
very considerable. The use of rapid-fire guns is, then, a very good
stroke of business, everything considered.
Again, when a submarine is chased and has no time to dive, she is in a
bad way, for she is not fast enough to escape, nor can she stop long
enough to aim a torpedo at her foe. It is easy to see, then, why her
armament[23] should and does include a couple of rapid-fire guns.
=The Need of a Quick-Action Gun.=—With these conditions staring them in
the face, the designers of submarines have worked hard to equip their
craft with not only rapid-firing but, what is equally as important,
_quick-action_ guns.
To get a rapid-fire machine gun was easy, for this type had been built
by the Maxims these many years; but to get one that could be swung or
lowered under the deck so that it would not offer resistance to the
water when the submarine was running submerged, and then brought up and
into action quickly, was quite a different thing, and inventors are
still at work on it.
By this I do not want you to take it that submarines are not provided
with rapid-fire and quick-action disappearing guns at the present time;
and should you or I take a look at them we would say that they are 99
per cent. perfect and that there is no need for further improvement.
But that is because we are neither designers, nor builders, nor
officers of undersea craft; and do not forget, either, that better
things are always in order.
Now, there are two kinds of rapid-fire, quick-action guns used for
submarine armament and these can be told from each other by the way
they are brought into action. They are (1) the _spring_ action gun, and
(2) the _compressed-air_ action gun.
=The Spring Action Gun.=—This type of submarine gun is made by the
Krupps of Essen, Germany, who now are building the U-boats for the
Central Powers.
This gun is mounted on the deck, over an opening in it called a
_deck-well_, and this arrangement allows the gun to be stowed away in
it. This is done to get rid of the resistance the water would have on
the gun if it remained fixed on deck when the boat is running submerged.
Although the deck-well is closed with hatches it is not watertight, and
the fittings, such as the sights and range finders, are taken off to
keep them from rusting when the gun is in the well.
A diagrammatic sketch of the gun and its housing is shown in Fig. 46;
the gun is mounted on a swinging frame by _trunnions_, and the frame is
fixed to a pedestal. A strong spring in the bottom of the well supplies
the power needed to throw the gun up and bring it into position.
When housed in the well the gun lays on its back, as shown by the
dotted lines, and this presses down on the spring. The tension of the
spring is enough to force the gun up and into place the instant the
catch which holds it is released.
[Illustration: _Courtesy of Scientific American_
A 3½ INCH SUBMARINE GUN IN ACTION SHOWING THE DECK WELL AND MANNER OF
OPERATION]
The sights and other attachments are fixed on the gun after it is
brought into position and the whole operation of raising the gun from
its well and putting on the fixtures takes just 20 seconds.
[Illustration: FIG. 46. HOW THE KRUPP OR GERMAN SUBMARINE GUN IS
MOUNTED.]
These guns have a bore of 75 _millimeters_[24]—equal to 3 inches—and 88
_millimeters_—equal to 3½ inches—respectively, and the shells they use
weigh in the neighborhood of 25 pounds.
=The Compressed Air Action Gun.=—This kind of submarine gun is used on
British undersea boats. It is mounted over a deck-well but inasmuch as
the gun is lowered into the well with all the fittings on it the well
has to be made watertight.
If you will look at Fig. 47, you will see how the gun is brought into
action. When compressed air is turned on in the cylinder, it forces the
plunger on which the gun is mounted up above the level of the deck.
The gun is fitted with fixed sights and a range finder, and is ready
for use the moment it has been brought into place above the deck, the
whole operation taking only 5 seconds.
[Illustration: FIG. 47. BRITISH AND AMERICAN-STYLE DECK GUN.]
The guns of the Allies’ submarines have bores of 3 and 4 inches, and
each one weighs nearly a ton. As a protection from enemy aircraft they
have a wide range and can, if needs be, fire a shot at 90 degrees, that
is, straight overhead.
=How a Submarine Lays Mines.=—The dangerous work of laying mines in an
enemy harbor by a submarine is not as spectacular as torpedoing ships
but it is an important part of the business of undersea craft.
A harbor which has been planted with mines to keep out enemy ships or
blow them up if they try to enter it is often remined overnight by
enemy submarines, and in this way a great deal of damage can be done to
friendly shipping.
But whether the submarine is used for mining its own or enemy harbors,
the outstanding feature of its work is that it does it all under water
and therefore the operations cannot be seen by spying eyes.
As we said in Chapter III, the mines are stored in a compartment in
the hull of the submarine and this can be shut off from the other
compartments by a bulkhead door. It also has a hatch opening through
the hull to the water outside, just as the door of a kitchen opens into
the back yard.
When the submarine has made its way under water to the place where the
mines are to be planted, the hatch is opened and the mine compartment
is allowed to fill with water. A mine layer in a diving suit can then
get in and out of the flooded compartment, take the mines one by one
through the open hatch, and place them in position.
Then there are mines which do not need to be set by a mine layer;
these are simply dropped through the hatch into the water and adjust
themselves as to depth. Other mines are made that are shot from the
torpedo tubes by compressed air and these are used for mining an enemy
harbor where the risks of having the submarine blown up is altogether
too great to take the chance.
=Kinds of Submarine Mines.=—Submarine mines—that is, mines that are
planted in harbors and other seaways, either as a protection from enemy
ships or as an offensive measure to blow them up—really have nothing to
do with submarine boats except that the latter are used to lay them.
But you ought to know about submarine mines, anyway, and so we’ll
digress a little and tell you something of them.
First of all, there are two distinct kinds of mines and these are, (1)
_contact mines_, and (2) _electrically controlled mines_.
As you can tell by its name a contact mine is one that is exploded
by the hull of a ship coming in contact with it—that is, by running
against it. This is the kind of mine that is most often laid by the
submarine.
An electrically controlled mine is one that is exploded by electricity.
For this purpose a pair of wires are connected to it and these lead
along the bottom of the harbor to two _observation stations_ on the
shore; when the enemy ship gets directly over the mine the observers
close the electric circuit and the mine is exploded.
This is the way the _Maine_ was sunk in Havana harbor in 1898, but
the _Maine_ was not an enemy ship. The result of this rash bit of
foolishness led to the war between the United States and Spain, and the
loss of her island possessions.
=How the Mines Are Made.=—_The contact mine._—This kind of a mine
consists of a steel shell, or container, which holds the charge of high
explosive, the trigger mechanism which explodes it when a ship strikes
it, and the weights and cables needed to sink the mine to the right
depth. Air chambers are also placed inside the container, to give the
mine buoyancy; otherwise it would sink at once to the bottom of the
sea.
[Illustration: FIG. 48. A SIMPLE CONTACT MINE.]
In the contact mine the detonator is formed of an arm, or lever, called
a _striker_, and this projects through the shell to the outside. When
a ship strikes the arm it drives a _firing pin_ against a _percussion
cap_ and explodes it, and this in turn fires the explosive charge in
the mine. (See Fig. 48.)
_How the Contact Mine Works._—The way the mine works is like this:
Before it is taken out of the compartment of the submarine it is
adjusted to float at the proper depth.
When the mine is in the water a weight that it carries is released and
sinks to the bottom; the cable which connects the weight and the mine
together holds the mine in the right position, while the air tanks in
the mine make it rise as high as the cable will let it go, as shown in
Fig. 49.
After the mine is planted, the submarine steals silently and invisibly
away. When an enemy ship—or any other, for that matter, for the contact
mine is no respecter of ships—strikes the trigger of the mine, it
explodes the charge, and there is one less ship to sail the turquoise
seas.
_The Electric Controlled Mine._—To the end that a harbor can be planted
with mines which will blow up enemy ships and yet be harmless to
friendly ships, mines fired by electricity from the shore were invented.
[Illustration: FIG. 49. HOW THE MINE ADJUSTS ITSELF.]
Mines of this kind are made about like contact mines in that they
contain an explosive charge and a detonator, but they are much larger
and far more powerful, for they have to be laid on the bed of the
harbor, and instead of being fired by a pin striking a percussion cap
they are fired by an electric spark.
From each mine laid in the harbor a pair of insulated copper wires
run to the shore, and this electric circuit connects with two shore
stations at a distance apart and which with the mine form a triangle.
The electric circuit has a key in it at each shore station, and to
explode the mine both of these keys must be pressed down at the same
time.
[Illustration: FIG. 50. HOW THE ELECTRIC MINE WORKS.]
Each shore station has a telescope fixed in position so that its _line
of sight_ (shown by the dotted lines in Fig. 50) passes directly over
the mine. Now when an enemy ship approaches, each observer will see it
when it sails on or across his line of sight and he will press his key.
But it is necessary that _both_ observers see the ship at the _same_
time that it is at the point where their lines of sight cross, and
consequently directly over the mine, and when this happens they will
both press their keys, the circuit will be closed, the electric current
will fire the mine, and the ship will change her course to one straight
up and speed with all possible haste to the port whence no ship ever
clears again.