HOW A REAL SUBMARINE IS MADE AND WORKS
AS we told you in the first chapter, there are two kinds of undersea
boats. These are (1) the Holland, or _submarine_ type, and (2) the
Lake, or _submersible_ type. Now, the Holland boat has a shape very
much like a cat-fish—that is, it has a blunt round head—and hence it
can dive easily; while the Lake is shaped more like an ordinary boat
and has a large _superstructure_, as that part above the _hull_[16] is
called, and this makes it easier for the Lake to _submerge_—that is,
sink on an even keel.
As the art of undersea boat building moved on apace, the two kinds of
craft began to lose their original distinctive features and were merged
into a single type. This was done to get a boat that was as strong and
as speedy as and could dive like the Holland, and to have at the same
time a boat that was as fast and as seaworthy on the surface as the
Lake.
This is the reason that most of the undersea craft of to-day are a
cross between the two kinds. In the older boats, though, the difference
is still marked; but the machinery of both is just about the same,
and consequently what we shall tell you of one is just as true of the
other, and from now on we shall call both kinds simply _submarines_.
=The Parts of a Submarine.=—To begin with, a submarine is formed
of: (1) the _hull_; (2) the _superstructure_, which is built on the
hull; (3) the _steering apparatus_, which includes the submerging and
diving devices; (4) the _power plant_, which consists of the engines,
the dynamo-motors, and the storage batteries, all of which drive the
submarine when it is on the surface and under the water-line.
As the power plant is a most important part of the anatomy of a
submarine, it will need a whole chapter to describe it the right way,
and this will come next. Now I’ll start in and tell you about the other
parts of the submarine.
=How the Hull Is Made.=—The hull is made of thin but very strong sheets
of steel riveted together. As the pressure of the water on it amounts
to 187 pounds to the square inch, at a depth of 300 feet, it must be
well braced or else there would be the unpleasant possibility that it
might be crushed in. As a rule, though, a submarine never travels at a
depth much greater than 100 feet.
Now, there are really two classes of submarines: (a) those that are
built for coast patrol cruising, and (b) those that are built for
trans-oceanic going.
A submarine of the first kind seldom has rough weather to contend with,
and so she need not be built as strong as one that is designed for
ocean going. She also has a slightly different shape from the latter,
in that she has a round cross-section, as shown in Fig. 23.
[Illustration: FIG. 23. CROSS-SECTION OF COAST-GOING SUBMARINE.]
By looking at Fig. 24 you will see that the ocean-going submarine
is more nearly half-round; this tends to prevent her from rolling
unduly. She also has a double hull which is divided into watertight
compartments to protect her from sinking should an enemy ship ram or
fire on her. The compartments are used as stowage tanks for fuel, etc.,
and so the space between the inner and outer _skins_, as the hulls are
called, is not wasted.
A large number of fittings are fixed to the hull, such as the _diving_
and _steering_ rudders (all of which will be described later), while
the superstructure is built on top of it.
=What the Superstructure Is.=—The _superstructure_ consists of (1) the
deck and (2) the conning tower. In the Holland submarine the deck is
only about one-third as long as the boat and this allows it to dive
easily.
[Illustration: FIG. 24. CROSS-SECTION OF OCEAN-GOING SUBMARINE.]
The Lake boat is decked over nearly the whole length of the hull. In it
are fitted rapid-fire guns which disappear, and there are watertight
ventilators which let in fresh air when the boat is traveling on the
surface. Further there is a _hatch_—that is, an opening in the deck
with a watertight door—through which the torpedoes can be lowered into
the _hold_ of the submarine.
=The Outside of the Conning Tower.=—From out of the center of the deck
rises the _conning tower_. This is a heavily armored, shell-proof,
circular structure, from which the captain makes his observations
and sends his orders down into the engine-room and controlling
compartments. On the bridge or upper deck of the conning tower is a
hatch by which the crew can get into and out of the boat.
A steering wheel and compass are fixed to the outside of the conning
tower, and the submarine can be steered by these when it is running on
the surface. A stanchion for carrying the signal lights is also secured
to the conning tower; while the _periscope_, or eye of the submarine,
passes through the bridge and to one side of the hatch. Of this
wonderful instrument we shall have much to say a little further on.
Wires, or _stays_, as they are called, fore and aft are used to brace
and hold the periscope and signal stanchion firm against the force of
the water which presses on them when the craft is submerged and under
way. The tops of the signal stanchion and the periscope are also braced
by a _signal halyard_, which is simply a wire, or cable, stretched taut
between them.
On all modern submarines a _wireless aerial_ is attached to a mast
which can be folded down flat on the deck when the submarine is getting
ready to make a dive.
=A Look Inside of the Hull.=—Now let’s take a look inside of the
submarine. The whole hull is divided up into a number of watertight
compartments, any one of which can be shut off from the others and so
lessen the danger of sinking by ramming or by shell-fire, should the
boat be afloat. In these compartments are placed all the machinery and
the controls for operating the submarine.
These various compartments are: (1) the conning tower; (2) the
navigating compartment; (3) the engine and dynamo room; (4) the fore
and aft storage battery rooms; (5) the fuel tanks; (6) the diving
control compartment; (7) the fore and aft ballast tanks; (8) the water
pumps; (9) the fore and aft high pressure air flasks; (10) the high
pressure air compressor; (11) the torpedo compartment; (12) the mine
compartment; (13) the trimming tanks; (14) the quarters of the crew;
and (15) the quarters of the officers. All of these are clearly shown
in Fig. 25.
The watertight doors of these compartments are worked by _worm_ gears,
driven by electric motors, as shown in Fig. 25, and any of the doors
can be opened or shut by merely throwing a switch.
=A Peep into the Conning Tower.=—The free space inside of the conning
tower is not more than 8 feet in height and 10 feet in diameter.
Sticking down through the deck for about 2½ feet is the periscope, or
two of them, for all submarines now built are fitted with a pair of
them so that should one of them be hit and put out of business the
other will be available.
[Illustration: FIG. 25. THE MAIN PARTS OF A SUBMARINE.]
This instrument is formed of a long tube with a hood at the upper end,
which is outside of the conning tower, and an elbow at the lower end,
inside of the tower. An eye-piece is fixed to the lower end, so that
the captain can scan the horizon at all times. How a periscope is made
and used will be described in a later chapter.
Just below the eye-piece of the periscope is the underwater steering
wheel, and close to and to one side of the latter is the underwater
compass. In the more recent submarines a _gyroscopic compass_[17] is
used as well as the regular magnetic compass because the gyroscopic
compass is not affected by stray magnetic lines of force. Besides, a
_gyro_ compass, as it is called for short, points to the true north
instead of to the magnetic north pole, and a true compass is of the
greatest importance in guiding the submarine at night or when it is
submerged, for it is then as blind as the fish in Mammoth Cave.
Around the inside of the tower near the bridge are placed _ports_
through which the captain makes and takes his observation when the boat
is afloat. Within easy reach of his mouth are _speaking tubes_ which
lead to the engine, diving, and torpedo compartments. The captain also
has at his finger-ends an electric signal system of lights and bells,
which he operates by push buttons and switches.
So you see he can get into instant touch with all the vital parts of
his boat. He also has full control over the trimming tanks and the
storage batteries, both of which I shall tell you about in detail
presently.
[Illustration: _Courtesy of Scientific American_
THE CONNING TOWER (UPPER) AND NAVIGATING COMPARTMENT (LOWER) CONTROLS
OF A MODERN SUBMARINE]
Right in the line of sight of his eyes is a _depth meter_ by which he
can see at a glance at just what depth his craft is moving, and he can
also see at what _angle_[18] the diving rudder, or _elevator_, as it is
called, is set.
A compartment _tell-tale_ (a numbered chart showing each compartment
of the boat) also hangs in sight, and if a compartment should begin to
leak it is instantly indicated by the tell-tale, which in this case is
a miniature electric lamp that lights up back of the number.
By pressing a button he can ring an electric bell in the leaking
compartment and so warn the crew that he is about to close the
electrically operated _bulkhead_ door and so shut the compartment off
from the rest of the boat if the damage done is so serious that it
cannot be repaired.
=Now the Navigating Compartment.=—As you have read before, the conning
tower is not a part of the hull but of the superstructure. Now, when
the captain or any of his crew wants to get from the conning tower into
the hull of the boat he must do so through a hatch in the lower deck
which is exactly like the hatch in the top or bridge of the tower.
This arrangement makes it easy to shut off the conning tower into the
rest of the boat if it should be seriously damaged by shell-fire or
by collision. Should this happen, the boat is steered from another
compartment called the _navigating room_, in which are all of the
devices used in the conning tower. So you see there are two complete
navigating rooms and an outside deck control by which the submarine can
be steered and operated, no matter how badly damaged she may be.
=Next, the Diving Control Compartment.=—The compartment containing the
_diving control_, by means of which the submarine can be made to dive
and to come to the surface, is fitted with the following devices:
First, there is the _diving wheel_, which works the horizontal or
diving rudders.
Next, there is the _angle indicator_, which is simply a _quadrant_—that
is, a quarter of a circle—marked off into degrees and each degree into
quarters. It has a needle which moves over the quadrant as the pilot
turns the diving wheel and this indicates the number of degrees up or
down the horizontal rudders have moved.
Another instrument is the _depth indicator_.
Then there is also an indicator which is merely a modified form of a
carpenter’s _spirit_ level. This little device shows when the craft is
running on an even keel and when it is running with its keel inclined.
For instance, should the diving rudder fail to respond to the touch of
the man at the wheel, the level would indicate it, as would also the
depth indicator.
Other fittings are the levers and the valve controls, by means of which
water can be let into the ballast tanks.
Now, before I explain how the submarine is made to dive and how the
ballast tanks work, or, rather, the other way about, I want to tell
you a little about the why and the wherefore of these very interesting
operations.
=The Four States of the Submarine.=—A submarine has four states, or
conditions, in which it exists in the water. These are (1) the _light_,
or surface cruising condition; (2) the _awash_, or partly submerged
condition; (3) the _submerged_ condition; and (4) the _totally
submerged_ condition—all of which is clearly shown in the diagram Fig.
26.
[Illustration: FIG. 26. HOW THE SUBMARINE SUBMERGES OR THE FOUR STATES
OF THE SUBMARINE.]
_The Light Condition._—The light, or cruising, condition is simply the
position a submarine takes when she floats on the water, due to her own
natural buoyancy, and it is exactly like that of any other ship.
While in this position the captain takes his observations from the
deck, if there is no danger of being hit by the enemy; but if there
is danger, he then makes his observations through the ports from the
inside of the conning tower.
_The Awash Condition._—This condition is not as natural as the one
just described, and it has to be done by means of the ballast tanks.
These are located fore and aft and they can be connected with, or
disconnected from, each other at will.
Now, when the captain wants to bring his submarine to the awash
condition an _inlet valve_, or _Kingston valve_ as it is called, is
opened and the sea-water then flows into these tanks, the amount and
velocity of the inrushing water being, of course, under control at all
times.
This extra weight destroys part of the buoyancy of the boat, and as
she gets heavier she sinks until nothing but her conning tower remains
above the water-line, the deck being awash. While in this condition
observations are taken either from the ports in the conning tower or
with the periscope, the object-glass of which has been lowered enough
to become useful.
_The Submerged Condition._—In this condition the periscope alone
remains above the water. It is had by allowing more water to flow
into the ballast tanks, thus destroying a little more of the craft’s
buoyancy, which makes her sink down until the conning tower is
completely submerged. It is in this condition that the captain makes
his observations with the periscope.
_The Totally Submerged Condition._—This is an exaggeration of the
submerged condition, and it is had by letting still more water flow
into the ballast tanks, thus sinking the submarine completely. The only
way to steer the boat when it is in this condition is, of course, by
means of the compass, for both the conning tower and the periscope are
totally submerged.
But do not mistake the term _totally submerged_ to mean that the
buoyancy of the submarine is _totally destroyed_; for such is not the
case during any stage of its submergence. You can easily see that if
the buoyancy were completely destroyed the submarine would then become
a dead weight and sink to the bottom of the sea, never more to rise.
Instead, when the submarine is totally submerged she can, by what
is known as her _reserve_, or _extra_ buoyancy, and about which you
will read later on, come to the awash or the light condition in a few
minutes by simply pumping the water out of the ballast tanks.
=How a Submarine Dives.=—Now let’s get back to the way a submarine
dives. In the first place, let us suppose the boat is running in
the light, or cruising, condition. An enemy ship is sighted and the
captain of the undersea craft gives orders to clear the deck and close
the hatches. Then he brings the boat from the cruising to the awash
condition, which is done as we have just described.
Next, he gives the order to the man at the diving wheel to make the
dive. He does not need to do this by word of mouth but he can use an
electric indicator which points out the angle at which he wants the
horizontal rudders set (see Fig. 27). Contrary, now, to what you might
expect, a submarine cannot dive at any angle, but it must make a very
shallow dive.
[Illustration: FIG. 27. FORE DIVING HORIZONTAL RUDDERS OR HYDROPLANES
OF A SUBMARINE.]
[Illustration: FIG. 28. HOW THE SUBMARINE DIVES.]
So when the order is given, the diving rudders are set at only ½ a
degree from the horizontal, as shown in Fig. 28. The craft must move
through the water at about 5 knots, which is the proper diving speed.
When the conning tower is one-fourth submerged the angle of the rudders
is increased to 1¼ degrees.
This angle is held until the conning tower is half submerged; and then
the angle is changed to 2 degrees, and it is held there until the
conning tower is three-quarters submerged. As soon as this takes place,
the angle is decreased to 1¼ degrees again, and the rudders remain at
this angle until the dive is completed.
_Why a Shallow Dive Is Made._—The reason such a shallow dive must be
made is the result of having to let water into the ballast tanks to
bring the craft to the awash condition before diving.
If the angle of the dive were to be suddenly increased to 10 or 15
degrees the tilting of the boat would throw all the water forward in
the tanks and this would seriously upset her balance, and might even
make her settle nose downward to the bottom of the sea.
_How the Boat Is Kept Submerged._—When a dive is to be made the diving
rudders are set at the angles just mentioned, but water is not let into
the ballast tanks at the same time, for this would also tend to destroy
the balance of the boat.
But when the captain wants to keep his submarine at a certain depth
below the surface of the water after the dive is made he has water
admitted to the ballast tanks and this keeps her at that level. When he
wants to return to the surface, or “break water,” the water is pumped
out and then the diving rudders are set and the boat makes an upward
glide.
_The Time It Takes for a Dive._—The time needed for a submarine to
get ready to dive is about 2 minutes; but this is often long enough
for it to become a target if a submarine chaser is on the little
war-dog’s trail. Should she be hard pressed she might dive at a steeper
angle—say, 5 degrees, but never more, and under ordinary conditions she
will never dive at more than 2 degrees’ inclination.
The reason it takes time for a submarine to get ready to dive is
because the wireless masts have to be folded in, the machine guns
disappeared, and the hatches fastened down. Finally, it must not be
forgotten that a submarine can dive only when she is pushing ahead
under power. If she is at rest and the captain wants her to sink he
must either start her engines or else be content to simply submerge her
on an even keel.
=The Ballast Pumps and What They Do.=—The pumps which pump the water
from the ballast tanks are driven by electric motors. They must be
powerful pumps, for they not only have to pump the water out of the
tanks quickly, but they have to force it out against the pressure of
water in which the submarine is submerged; this pressure increases the
deeper the boat sinks, and it is often 80 pounds or more to the square
inch. The pumps are controlled from the conning tower, and also from
the navigating compartment.
=What the Buoyancy Tanks Are For.=—We said previously that a submarine
never loses its buoyancy completely. If she were built like an
ordinary ship and simply fitted with ballast tanks, she would sink when
these are filled with water and never come up again, for her natural
buoyancy would be destroyed. As it is, a submarine has tanks filled
with air which keeps her buoyant, and these will bring her to the
surface the moment the ballast tanks are empty.
Make this experiment and you will quickly understand how these buoyancy
air tanks work: Take an empty bottle and cork it up tight. It looks
empty, but as a matter of fact it is filled with _air_. Push the bottle
to the bottom of a bucket of water; let go of it and the instant you do
so it will rise to the surface.
A large number of steel air tanks, or buoyancy tanks, or high pressure
_air-flasks_, as they are called, are placed both fore and aft in a
submarine, and these are filled with compressed air at a pressure of
2,000 pounds to the square inch. These air-flasks have a tremendous
supporting power—which is only another way of saying that they are
extremely buoyant.
It must be clear now that even though the submarine is resting on the
floor of the ocean it can always rise to the surface by the _reserve
buoyancy_ provided by these air-flasks.
=Compressed Air and Air-Compressor Pumps.=—The air-flasks are filled
with compressed air by _air-compressor pumps_ which are driven by the
engines when the submarine is running light or awash.
The air compressor is formed of several air pumps coupled together;
each air pump is made very much like a water pump, but it sucks the
air in from the outside and then forces it into the air-flasks until
it is under a pressure of 2,000 pounds to the square inch. To overcome
this _back pressure_, as it is called, the pumps must be extra powerful.
These pumps also supply compressed air for the torpedo tubes, the
trimming tanks, and to help blow out the water from the ballast tanks.
=Inside the Torpedo Compartment.=—The torpedo compartment contains
the extra torpedoes in their cradles. Near the tubes from which the
torpedoes are shot is the compressed air which furnishes the propulsive
power needed to make the torpedoes leave their tubes.
=Why Trimming Tanks Are Used.=—As a torpedo weighs nearly 1,000 pounds,
it is plain that whenever one is shot from the craft it will very
greatly disturb the balance of the boat unless some means is used to
add weight to it which is exactly equal to the weight of the torpedo.
This is done by what is called the _trimming tanks_. These are usually
placed fore and aft and in or near the torpedo and mine compartments.
As soon as a torpedo is shot, or a mine is laid, the trimming tanks
are filled with water which makes up for the weight lost and keeps the
craft on an even keel.
If, on the other hand, any extra weight is taken aboard the submarine,
enough water to equal it is blown out by compressed air.
=In the Mine Compartment.=—The mine, as the stationary bombs that are
to be laid in a harbor or some other _strategic_ point are called, are
kept in the mine compartment.
This compartment has a trap door in it through which a _mine-layer_,
that is a man dressed in a diving-suit, can get out of and back into
the submarine again, or through which the mines can be lowered.
[Illustration: FIG. 29. MUSHROOM ANCHOR.]
=And Last of All, the Sea Anchor.=—A submarine must have an anchor as
well as a merchantman. The anchor is of the _mushroom_ type, so called
from its appearance; and as you will see from the accompanying picture
(Fig. 29), it is very different from the two armed and fluked kind that
so resembles an Irishman’s anchor i.e., a pickax.
=Where the Crew of a Submarine Lives.=—Proper quarters for the officers
and crew in the earlier submarines were sadly neglected; but conditions
have greatly changed since then—though of course they are not quite so
good as living in a luxurious hotel ashore.
Great improvements have been made in behalf of the undersea navigators
and sailors, until in the more recent submarines the crew have quarters
that compare favorably with those on board a battleship.
There are oxygen tanks that supply pure air, while electric fans set up
a forced draft and keep the air cool and make it circulate freely. Then
there are electric heaters which keep the temperature just right under
all conditions.
It goes without saying that the modern submarine has its _galley_—that
is, its cook room. But, very different from the galley on the old
windjammers that used to sail the seas, the sea-cook does not use a
cook-stove, which was also called a galley, but electricity.