THE MECHANISM OF THE SUBMARINE, AND SUBMARINES OF THE FUTURE
Mr. H. G. Wells, in his “Anticipations,” confesses that his imagination,
in spite even of spurring, refuses to see any sort of submarine doing
anything but suffocate its crew and founder at sea. “It must involve
physical inconvenience of the most demoralising sort simply to be in one
for any length of time.... You may of course throw out a torpedo or so
with as much chance of hitting vitally as you would have if you were
blindfolded, turned round three times and told to fire revolver-shots at
a charging elephant.... Given a derelict ironclad on a still night
within sight of land, a carefully handled submarine might succeed in
groping its way to it and destroying it; but then it would be much
better to attack such a vessel and capture it boldly with a few
desperate men on a tug. At the utmost, the submarine will be used in
narrow waters, in rivers, or to fluster or destroy ships in harbour, or
with poor-spirited crews—that is to say, it will simply be an added
power in the hands of the nation that is predominant at sea. And even
then, it can be merely destructive, while a sane and high-spirited
fighter will always be dissatisfied if, with an undisputable superiority
of force, he fails to take.”
[Illustration:
INTERIOR OF THE FIRST BRITISH SUBMARINES (NOS. I.–V.).
]
We are afraid that Mr. Wells has not taken the trouble to keep himself
in touch with the latest developments of submarine navigation. As we
write, news comes from America of a party who spent fifteen hours under
water in the _Fulton_ without suffering any inconvenience. This does not
look much like the “suffocation” Mr. Wells anticipates. As to
torpedo-firing, French and American boats whilst under way have made
excellent practice, both at stationary and at moving targets; while in
making the assertion that the submarine will be used in narrow waters,
in rivers or in harbours, it is evident that Mr. Wells is unaware of the
lengthy voyages made by some of the newest boats.
The _David_ represented the best type of under-water vessel in the
sixties; that she is infinitely inferior to the newest _Holland_ type or
some of the French vessels of to-day goes without saying, and it will
not be surprising if the submarine of thirty years hence bears the same
resemblance to the _Holland_, as the _Holland_ does to the _David_.
The ideal submarine boat has a speed as great as that of the fastest
torpedo-boat, a very wide radius of action, excellent sea-keeping
powers, unlimited quantities of air for power and for respiration by the
crew; a means of directing its course by vision upon a moving object
whilst itself remaining invisible beneath the surface, and is very
habitable and comfortable for long periods of time.
The submarine of to-day lacks most of these attributes. It has a slow
rate of speed, whether on the surface or submerged, a narrow radius of
action, poor sea-keeping powers, a strictly limited quantity of
compressed air, and is absolutely blind when beneath the waves. Thus it
differs greatly from the ideal boat as sketched above, but its gradual
improvement may be safely predicted.
We propose in this chapter to describe, in simple language, the working
of a vessel intended for under-water navigation, and to consider what
improvements are likely to take place.
Every submarine boat worked by a crew must of necessity be capable of
floating on the surface of the water. This is a self-evident
proposition, for the crew must have means of ingress and egress, and the
only practical way of entering and leaving the boat is by an opening in
the hull when she is on the surface.
We have no doubt that the files of the Patent Office would show that
many inventors had designed boats which would sink to a certain depth
directly they were placed in the water. While in such a system no time
is lost in submersion, there would undeniably be difficulties in the way
of coming to the surface, &c.
The first problem, then, which confronts the designer of a submarine
boat is to find the most suitable method of sinking it to the depth at
which it is intended to navigate.
The most fundamental law of hydrostatics, which applies to all floating
bodies, and is equally true of wholly submerged vessels floating at any
depth, as of ships of ordinary form, floating on the surface, having
only a portion of their volume immersed, is that a ship floating freely
and at rest in still water must displace a volume of water having a
weight equal to her own weight.
The “displacement” of a vessel is defined as the weight of water
displaced, which is equal to the weight of the vessel and that of her
lading. A ship floating on the surface “displaces” a certain weight of
water; in order to force her beneath the surface two methods are open.
In the first place, her weight is increased by the introduction of water
ballast; thus her “displacement” is altered and she sinks until her
weight is again equal to the volume of water displaced.
In the second, the weight of the boat remains constant, but the
displacement is altered by the drawing in of “cylinders” or “drums;”
thus she sinks until her displacement again equals her weight.
The first inventor to employ the latter method was André Constantin, who
built a vessel during the siege of Paris, which was furnished with
pistons working in two cylinders; on these being drawn in from the
interior the boat sank to the required depth. The actual trials were,
however, not satisfactory. The _Nautilus_, of Messrs. Campbell & Ash,
which underwent some trials in Tilbury Docks in 1888, depended also on
the pulling in of cylinders (ten were employed, five on each side of the
vessel), for her submersion; the results were equally discouraging, and
some eminent men nearly lost their lives owing to the erratic behaviour
of this craft.
[Illustration:
THE SUBMARINE OF ANDRÉ CONSTANTIN.
(1874.)
]
No serious ship-constructor would nowadays think of adopting this method
of submersion, and we may therefore pass on to consider those which are
brought to the submerged condition by the admission of water into
special reservoirs or tanks.
Submarine boats so far as their immersion is concerned may be divided
into two classes.
1. Those which when submerged possess no floatability.
2. Those which in the same condition possess a small reserve buoyancy or
floatability.
Modern submarines almost without exception belong to the second
division, as this class has been found to possess great advantages over
the first.
1. SUBMARINES WITH NO FLOATABILITY WHEN SUBMERGED.
[Illustration:
“GOUBET II.”
]
Boats belonging to this division possess when submerged a total weight
equal to the weight of water displaced. During immersion it has been
found necessary to make the weight of the vessel and its contents
slightly exceed the weight of water displaced by the total volume of the
vessel; this excess of weight causes a downward motion which rapidly
accelerates unless checked, and care must be taken to regulate, either
automatically or otherwise, the depth, lest the vessel sink to a depth
where the pressure is greater than she can withstand.
[Illustration:
M. GOUBET ABOUT TO GO UNDER WATER IN HIS BOAT.
]
Although M. Goubet is a believer in the “no-floatability” idea, it has,
for some time past, been regarded with disfavour. Theoretically it is
possible to navigate a submarine whose total weight equals the weight of
water displaced so that she keeps at a given level without rising or
sinking, but the system will not work satisfactorily when put to severe
and prolonged tests. It is found to be impossible to obtain perfect
equality between the two weights: submarine currents, variations of
atmospheric pressure and temperature, and movements inside the boat all
tending to disturb its equilibrium.
2. SUBMARINES POSSESSING FLOATABILITY WHEN SUBMERGED.
Mr. Nordenfelt realised the superiority of submarines possessing a
reserve buoyancy when submerged over those which possessed no buoyancy
and all the most important of latter-day submarines fall under this
division.
It is quite obvious that should any accident happen, such as the entry
of water, the failure of the machinery, the asphyxiation of the crew
(rendering the detaching of a false keel impossible), &c., the submarine
with a reserve buoyancy would at once rise to the surface, while the
boat with no floatability would remain where it was and then gradually
commence to sink, owing to the fact that it is almost impossible to
prevent the water from finding its way, little by little, into the boat.
Submarines which possess floatability when submerged have a weight which
is less than their displacement and some mechanical action must be
resorted to to force them below the surface. The first operation
consists in introducing a certain amount of water into the tanks so that
the boat is brought to the “awash” condition, with the greater part of
the hull below water and only the conning tower, &c., appearing above
the waves. The complete submersion of the vessel may be attained in two
ways: either screws on vertical shafts are employed to “screw” the
vessel below the surface, whether at rest or whilst moving; or
horizontal rudders, or planes, are used to steer the boat below the
surface; this latter method is only applicable to moving vessels.[3]
Footnote 3:
A system of moving weights was employed by Drzewiecki and other
inventors.
IMMERSION BY SCREWS MOUNTED ON A VERTICAL SHAFT.
Just as a ship is driven backwards and forwards in the horizontal plane
by means of a screw or screws mounted on a horizontal shaft, so it is
possible to drive a ship up and down the vertical plane by means of one
or more screws immersed in the water and mounted on a vertical shaft;
the boat is by this method literally “screwed down” into the liquid.
The principle of the vertical screw was adopted by Bushnell who, in the
description of his submarine vessel, writes: “At the top there was
likewise an oar for ascending and descending or continuing at any
particular depth.... When the skilful operator had obtained an
equilibrium (by means of the forcing pumps) he could row upwards and
downwards or continue at any particular depth with an oar placed near
the top of the vessel, formed upon the principle of the screw, the axis
of the oar entering the vessel. By turning the oar one way he raised the
vessel, by turning it in the other he depressed it.”
[Illustration:
PROFESSOR TUCK’S SUBMARINE.
(1884.)
]
M. Gaget remarks that “it is very strange that Bushnell should have
discovered and concealed with so much care the instrument of propulsion
which Sauvage studied and introduced fifty years later.” The fact is, of
course, that the principle of the screw-propeller was known in the
seventeenth century and that in May, 1785, Joseph Bramah patented a
screw-propeller, identical in general arrangement with those in use
to-day. The first practical use of the screw was made by John Stevens,
who in 1804 launched a steamboat eighteen feet long by fourteen feet
beam with a direct acting high-pressure engine having a tubular
boiler—and driving a screw with four blades. Although the principle of
the screw for ship propulsion was thus recognised at this early period
it was not till the thirties (of the nineteenth century) that the
screw-propeller succeeded in attracting the attention of the engineering
world.
Professor Tuck in his boat (1884) placed the propeller directly beneath
the centre of the hull, so that it should submerge on an even keel.
Mr. Nordenfelt used vertical screws, which at first he fitted in side
sponsons, but afterwards in the fore and aft line, and considered it
absolutely essential that a diving boat should be kept horizontal when
being submerged, as any inclination downwards with the impetus of a
heavy boat would, he considered, almost to a certainty carry the boat
below its safe depth, before it could be effectually counteracted by
shifting weights. Such a theory was soon shown to be founded on a
misapprehension.
Some inventors (Waddington, Baker, &c.) have used four screws operating
in pits equidistant from the centre of the boat, two on the upper part
and two on the under part, but all such methods have been discarded in
the newest designs.
IMMERSION BY HORIZONTAL RUDDERS.
The ordinary vertical rudder steers the ship either to port or starboard
in the horizontal plane, and the horizontal rudder can be used similarly
to control its position in the vertical plane.
This method of steering a boat beneath the surface by the inclination of
horizontal rudders is, of course, only applicable when the boat is
moving.
The position that the horizontal rudder or rudders should occupy is a
question about which much has been written, and opinion appears to be
still divided on the subject. Some hold that they should be placed at
the stern, others that they should be placed on either side of the
vessel, and these latter again differ as to whether they should be
forward, amidship, or aft. In spite of all the arguments in favour of
placing the rudders forward, Captain Hovgaard considers that this
disposition can hardly be recommended except in very long boats where it
may prove a necessity. The _Gustave Zédé_ has six diving rudders, two
forward, two in the centre, and two aft; whilst in the _Narval_ class
there are four rudders, two forward and two aft; the _Holland_
submarines have aft rudders only.
_Control in the Vertical Plane._
That beautiful machine, the Whitehead torpedo, is maintained at a set
depth below the surface by means of a pendulum and a hydrostatic valve
which regulate the horizontal rudders, and also in its true course by
the gyroscope. In the case of the submarine it is necessary that it
should not pass a certain limit when on its downward course, and that it
keep so far as is possible the same level throughout its run under
water.
The control of the submarine in the vertical plane may be accomplished
by the manipulation of the rudders, either automatically, by means of
some such arrangement as the hydrostatic valve or pendulum, or by hand,
and she can be kept on an even keel and prevented from rising to the
surface or sinking to the bottom, when running beneath the waves, by the
pumping of water from a reservoir situated aft to one situated forward,
or vice versâ, by the admission of water into trimming tanks, by
shifting weights, &c. These operations can be carried out either
automatically or by hand-operated mechanism.
It will be readily understood that while it is a comparatively simple
matter to force a vessel beneath the surface to a depth previously
determined, it is not so easy to ensure its keeping at this depth during
the whole time it is submerged and maintaining throughout the run a
perfectly even keel.
One of the greatest difficulties the inventor of submarine boats has to
overcome is their lack of longitudinal stability. Submerged vessels are
of two classes, those which are equal in weight to the water they
displace, and those which are lighter. Both classes are subject to
various disturbances which tend to upset their longitudinal stability
and send them up to the surface and down towards the bottom. In Chapter
XV. mention is made of the difficulties experienced by those who had to
navigate the Nordenfelt.
The principal causes of disturbance have been summed up by Captain
Hovgaard in a paper entitled, “The Motion of Submarine Boats in the
Vertical Plane,” read before the Institution of Naval Architects at the
Annual Meeting in 1901.
1. Faulty use of horizontal rudder. 2. Admission of water through
leakages. 3. Expulsion of foul air and products of combustion. 3a.
Firing of torpedoes and projectiles. 4. Movements of crew. 5. Existence
of free surfaces of liquid. 6. Movements of loose weights, such as fuel.
7. Variations of buoyancy caused by varying density of sea water. 8.
Grounding and collision. 9. Variations in speed.
Some of the most important of these disturbances may be briefly
discussed.
1. Most modern submarines are provided with more than one pair of
horizontal rudders, but if all the rudders should refuse to act and the
boat is running down an inclined plane, the only thing to be done is to
pump the water out of the tanks and thus bring the boat to the surface.
2. By the careful construction of the hull, and by strict control of all
sea-valves, the admission of water may be prevented. If the boat is
stove in and water enters in any quantity, she will inevitably sink. As
an escape some inventors have provided their submarines with detachable
boats.
3. Usually the length of the run under water will not be so great that
the foul air will need to be got rid of. If necessary it can be expelled
by drawing on the store of compressed air, and as the substances
withdrawn will always be small, no change in longitudinal balance need
be feared if precautions are taken. As all modern submarines are driven
by electricity beneath the surface, the expulsion of products of
combustion need not be considered.
3a. In the earliest submarine boats the torpedoes consisted of charges
of explosive in cases, which were attached to the outside of the vessel
to be attacked, or were towed against her sides.
Those who had little faith in the future of under-water warfare declared
that a torpedo could never be fired from a tube in a submerged vessel
without disastrous effects. The Nordenfelt boats were certainly not
successful in discharging torpedoes, for as a general rule they as
nearly as possible stood up vertically on their tails and proceeded to
plunge to the bottom stern first on these occasions.
However, since then, submarines have fired torpedoes quite
satisfactorily under water.
The expulsion of a torpedo from a vessel totally submerged in the water,
whether equal to or less than the weight to the water displaced,
naturally reduces her weight and tends to send her up towards the
surface. This tendency can best be counteracted by the admission of a
certain quantity of water ballast into the boat.
The method now usually followed is to allow the surrounding water to
enter the tube immediately after the launch of the torpedo, and as the
weight of the volume of water admitted will be about equal to that of
the missile ejected, the longitudinal stability of the submarine should
not be disturbed. When the second torpedo comes to be placed in the
tube, the volume of water already in it must of necessity be ejected,
and a compensating reservoir may be used to receive it. As each torpedo
is fired a certain amount of water, corresponding to the weight of the
projectile, must be allowed to enter the compensating reservoir. This
may be done automatically.
The _Engineer_ in a leader on January 18, 1901, said: “The discharge of
a bow torpedo (by a submarine) would be instantly followed by the rise
of the bow; relieved of the weight the boat would tend to stand on end.
If going ahead at the time she would immediately come to the surface to
be destroyed. If going astern she would plunge downwards and the
consequences might be equally serious.... Torpedoes must be fired when
the submarine is at rest.”
In spite of this dogma submarines have fired torpedoes whilst in motion
with success, and in modern submarines ample provision is made for the
loss of weight occasioned by the discharge of the torpedo.
4. Reference has been made to the fact that when the Nordenfelt boat was
moving along on an even keel, and a greaser walked forward a couple of
feet in his engine room, her head would go down a little, the water
would surge forward in the tanks, and she would plunge to the bottom,
unless checked in time. It has been said that one man going forward in a
submarine boat would cause her to dive to a depth of thirty-six feet in
one minute. The movements of the crew may be compensated for by
automatic arrangements, but the ideal method would be one in which every
one remained immovable at his post during the submerged run.
_Steering Below Water._
Quite early in the history of submarine navigation it was found that the
compass was not so reliable when the boat was navigating under water as
it was when she was on the surface. This is not to be wondered at, for
the compass of a submarine is placed in the interior of a tightly-closed
metallic shell and in close proximity to an electro-motor and powerful
currents capable of influencing it considerably, if not of rendering it
altogether useless.
The principal causes of the unreliability of the compass on a submerged
boat are:—
1. The currents normally produced by the electric motor.
2. The abnormal currents flowing in certain unknown parts of the hull
owing to lack of proper insulation.
3. The permanent or transitory magnetisation of the hull if made of a
magnetic metal.
The best position for the compass on a submarine has been a much debated
point, but it is now generally agreed to be in the centre of the hull.
The conning tower of the first British submarine was made of steel, but
it was afterwards replaced by one of brass.
M. M. Gaget in his book[4] states that so entirely untrustworthy and
impracticable has steering by compass in French submarines been found,
that the gyroscope has been requisitioned. He inclines to the belief
that this instrument is the best indicator of route that has yet been
devised, yet he points out the want of some reliable method by which the
distance made by a submerged boat could be gauged with accuracy.
Footnote 4:
“La Navigation Sous-Marin.”
MOTIVE POWER.
The question of the best method of propulsion for submarine boats must
be considered under two heads, namely, propulsion on the surface and
below the water.
It will be quite evident that the conditions under which a motor in a
submarine works differ according as the boat is running above or beneath
the surface; and we arrive at the conclusion that if the same motor is
to serve for both conditions special arrangements will have to be made
to permit it to work under abnormal conditions. Should this be found
impracticable a new method of propulsion will have to be found for
under-water travelling.
Every heat engine consumes both air and fuel (whether coal, oil, gas,
&c.), and the process of absorption of the fuel is accompanied by the
giving out of a certain weight of the substance in the form of gas.
Whilst the boat is proceeding beneath the water its weight is
continually being modified, and it is practically impossible to
compensate for this change by the addition of water to the reservoirs.
Besides this difficulty the combustion of the fuel not only absorbs a
large quantity of the air which is so precious a quantity in a submerged
vessel, but also sets free deleterious gases which naturally have
prejudicial effects on the health of the crew. It may therefore be
asserted that a submarine can only be propelled under water by means of
a motor capable of working without combustion or loss of weight. It
remains therefore to discover the most suitable method fulfilling these
conditions.
1. _By Mechanical Means such as Clockwork, Springs, &c._—The Howell
torpedo is driven by means of a heavy flywheel in the interior which is
spun up to 10,000 revolutions a minute before discharging by means of
special machinery. While all these methods are practicable they must be
put aside as unsuitable owing to the slowness of the speed which a boat
thus propelled can attain.
2. _Compressed Air._—In order that a submarine may be driven at a high
rate of speed for a considerable distance, such a large store of
compressed air would have to be carried if this method were adopted,
that little space would be left in the vessel for any other purposes. In
addition to this such a store of compressed air would be a source of
danger.
3. _Manual Power._—The earliest submarines were of course driven by hand
power, but no one nowadays would think of adopting this method.
4. _Steam from Heated Water._—Mr. Nordenfelt propelled his boats beneath
the surface by means of the steam given off by the heated water in the
cisterns, and this was found sufficient for a distance run of 14 knots.
He disliked accumulators, and this is not to be wondered at, for in his
time they were very far from perfect; were he designing a submarine
to-day, however, it is probable that he would choose electricity for
sub-surface working.
5. _Chemical Engines._—Dr. Payerne, d’Allest, and others, by means of a
_chaudière pyrotechnique_, burnt, in hermetically closed furnaces,
combustibles containing in themselves the oxygen necessary for their
combustion, and got rid of the products of combustion by ingenious
devices.
6. _Electricity._—All modern submarines rely on an electric motor for
under-water propulsion, the current being derived from accumulators. The
ideal primary battery and the ideal accumulator are still to seek, but
the latter improves yearly, and there is little doubt that some few
years hence the current available will enable the submarine to make long
voyages under water with greatly increased speed. It is said that the
_Holland_ has on no fewer than four occasions burned up the armature of
her motor, and some device seems to be wanted to keep the armature cool.
7. _Carbonic Acid._—Many attempts have been made to construct an engine
which can be worked by liquid carbonic acid, but the general result, as
some one has said, has hitherto been that the inventors have been more
or less broken up in body and mind.
8. _Liquid Air_ has been suggested as a propelling agent for submarines,
but up till now it has not been applied for such a purpose. A motor-car
propelled by liquid atmospheric air was shown at the Agricultural Hall
in April last, and some energetic Americans are endeavouring to “boom”
this elusive substance in this country. More sober investigators have,
however, little faith in an immediate commercial future for liquid air.
[Illustration:
INSIDE THE “GOUBET.”
]
PROPULSION OF THE SURFACE.
While the “Holland” boats for the British and United States navies are
driven on the surface by a gasoline engine, this type of motor has not
yet been used on the French boats, a steam engine fed with liquid fuel
being employed in the _Narval_ and vessels of this class, while in the
_Gustave Zédé_, _Morse_, &c., electricity is the sole motive power both
above and below the waves. _Le Yacht_ states that France has always
avoided the use of gasoline owing to the danger which arises from its
presence on board submarine craft.
[Illustration:
THE GASOLINE ENGINES OF THE FIRST BRITISH SUBMARINES.
]
(_a_) _The Steam Engine._—In the Nordenfelt boat steam was raised, when
running on the surface, by the burning of coal, but of late the advances
that have been made by the employment of liquid fuel have led to the
employment of this combustible for submarine boat propulsion in
preference to coal.
The great drawback at present to the use of the steam engine is the
length of time necessary for the unshipping of the chimney, the cooling
of the engines, &c.
(_b_) _The Oil Engine._—At the present time there is no oil motor in
existence of sufficient power to give even moderate speed to a large
boat, but the ingenuity of the engineer will probably overcome this
drawback.
Those who make the dogmatic assertion that the submarine boat cannot be
very fast because she cannot be endowed with much power, remind one of
the wiseacres who were so convinced that steamboats would never replace
sailing-vessels, nor steam locomotives the horse-drawn coach.
“The power required to impel a vessel through the water is augmented by
her submergence. If 5,000 1–h.p. are required to drive a displacement of
120 tons at 28 knots, then rather more power will be required to drive
120 tons wholly submerged at the same speed.”
This statement appeared in the _Engineer_ in the early part of 1901, but
it appears that an exactly opposite opinion is held by many eminent
authorities. For instance, at the discussion which followed the reading
of Mr. Nordenfelt’s paper on Submarine Boats at the Royal United Service
Institution in 1886, Mr. Anderson, C.E., stated that it was well known
through the late Mr. Froude’s investigation that a fish-shaped vessel
under water was in much more favourable circumstances for obtaining high
speed than any vessel on the surface of the water, because it had been
established theoretically that a vessel of easy lines completely
submarine met with no resistance at all except the skin friction of the
water, no resistance, that was to say, such as that which arose from the
bow wave.
Mr. Anderson went on to say that he believed that if Mr. Nordenfelt
would apply a little more ingenuity and perseverance to the perfecting
of his boat, the result would be the attainment of a very high speed
under water, and consequently a most formidable vessel. Mr. Nordenfelt
himself said that it was absolutely proved that the speed below for a
given consumption of fuel for a given boat must be greater than the
speed above, and Mr. J. J. Thornycroft recently explained to an
interviewer that the resistance is less for a completely submerged body
than one travelling on the surface, because no waves are created. “The
water that is displaced in front,” he said, “simply closes in behind and
helps to push the body forward. A boat moving on the surface throws out
waves in front and on either side, and that means an absolute loss of
energy. You will find that for this reason a ‘Whitehead’ torpedo travels
faster under the water than on the surface.”[5]
Footnote 5:
_Daily Graphic_, November 10, 1900.
ARMAMENT.
The armament of the boats designed by Bushnell and Fulton was a case of
explosive; the armament of the _David_ that sank the _Housatonic_ was a
spar-torpedo, but the armament of all modern submarines is the
automobile fish torpedo. Mr. Holland in his earlier designs provided his
boats with guns, but submarine cannon firing heavy shells have since
been discarded.
In the new British submarines one torpedo expulsion tube is fitted at
the extreme forward end of the vessel, opening outward 2 feet below the
light water-line. Five Whitehead torpedoes, each 11 feet 8 inches long,
are carried.
SAFETY AND HABITABILITY.
It may safely be said that no difficulty will be found in getting
sailors to form the crew of a submarine boat in time of war. Great
Britain, the United States, France, and other great naval Powers have
only to call, and hundreds of brave fellows will volunteer, however
great the odds against which they may have to fight. This being the
case, our naval constructors must see to it that every precaution is
taken to make the boats as safe and as habitable as possible.
The accidents to which a submarine is subject are many. The most serious
is passing the safe limit of depth. If she descends beneath this limit
the pressure will increase; her hull will be battered in; she will
diminish in volume; her downward course will be rapidly accentuated, and
there must inevitably follow the crushing in of the boat and the death
of the crew.
[Illustration:
THE ARMAMENT AND THE PERISCOPE OF THE “GOUBET.”
]
For every boat there is a limiting depth, beyond which she must not go.
While it is quite possible to construct a boat strong enough to resist
the pressure at depths of 50 fathoms and over, it will not be necessary
to go deeper than 5 to 6 fathoms, or enough to clear the keel of a big
ship. Still it will be well to give the boat a hull capable of resisting
pressures greater than those she will normally encounter. By means of a
hydrostatic valve or some similar arrangement, the submarine may be kept
from diving to too great depths.
It is said that the “Goubet” boats can withstand the pressure at a depth
of about 5,000 feet, or very nearly a mile beneath the surface; the
“Holland” boats can navigate with safety at 150 feet, a depth quite
sufficient for all practical purposes.
The French submersible _Silure_ was recently sunk to a depth of 134½
feet, and it was found that the hull was compressed to the extent of
1–25th of an inch. No inconvenience was felt by the crew greater than
that experienced at a depth of 20 feet.
Submarines possessing floatability have the power of rising to the
surface should any accident happen to the motive power, steering gear,
machinery, &c., and automatic arrangements are provided for working the
horizontal rudders in order to keep the boat on an even keel. Some
accident might, however, cause the boat to begin to sink, and the
advisability of the submarine carrying a false bottom or detachable keel
has been pointed out, as this could be dropped in an emergency, causing
the vessel to rise at once to the surface.
The vessel _Le Plongeur_ carried a detachable boat, and Captain Hovgaard
in his design also supplied such a boat. It was made to stand the same
pressure as the submarine itself, and rested on a saddle-shaped packing,
against which it was tightly pressed down by means of a number of clips.
Inside the packing was a circular door in the boat and a corresponding
and smaller one in the ship arranged in such a way that it was possible
to get up into the boat, close the lower lid in the ship, and then the
lid in the boat. This done, all the handles of the clips were turned and
the water would probably enter the space inside the packing, and if not
it might be made to do so through a small pipe leading from the outside
to the space, and provided with a stopcock. The boat would now have a
certain buoyancy, but would hang on in two main clips, placed one at
each end of the detachable boat on mechanical connection with each other
so that they could only be let go both at the same time, thereby
preventing jamming. When these clips were opened the boat would ascend
to the surface; communication with the vessel, if somebody should be
left behind, might be kept up by telephonic connection.
M. Goubet, M. Drzewiecki, and other inventors provided their vessels
with means for being propelled by the crew, working either oars or
pedals, in the event of the machinery failing to act.
Respiration, or breathing, is a part of the life of all organisms,
whether animal or vegetable. Air is taken into the lungs; the oxygen is
absorbed, while the carbonic acid is given back again to the atmosphere.
The respiration of human beings or animals in closed chambers to which
the air is denied access is not possible beyond a certain period. The
oxygen is sooner or later, according to the size of the chamber, used
up, and the air becomes so vitiated with the carbonic acid expelled by
the lungs that the vital functions of the body are arrested.
Many of the earlier submarine boats carried no reserve of air, as the
time that they were intended to remain under water was not long.
Reference is made in old writings to the “chymicall liquor” supposed to
have been used by Cornelius Drebbel to restore the purity of the air in
his under-water vessel, but what its composition was we shall never
know.
The air required for respiration in a submarine vessel may be supplied
in two ways.
1. By some chemical method which purifies and regenerates the vitiated
air.
2. By compressed air or oxygen carried in special reservoirs.
3. By pipes leading down from the surface to the submerged vessel
through which fresh air is drawn and the foul air expelled.
4. By the return of the boat to the surface and the taking in of a fresh
supply of air.
Such substances as caustic soda, lime, bromide of magnesium, &c., are
capable of absorbing carbonic acid, and have been used, but modern
submarine vessels rely on compressed-air compartments. M. Calmette, in
his account of his voyage under water in the _Morse_, says that thanks
to the labours of a commission formed by M. de Lanessan the difficulty
of respiration has been satisfactorily overcome, with the result that
the crew can remain for sixteen hours under water without the slightest
strain. This may refer to the discovery by M. Georges Jaubert of a
chemical substance of comparatively light weight which in one single
operation can not only completely remove from vitiated air the carbonic
acid, water vapour, and other non-respirable products, but can also
automatically restore to it in exchange the exact mathematical quantity
of oxygen which it lacks. In other words the substance when placed in
contact with air vitiated by respiration can completely regenerate it
and restore to it its original qualities. This wonderful substance, the
composition of which has not yet been made public, has been the subject
of some communications by Dr. Laborde to the Paris Academy of Sciences.
In these it is mentioned that experiments were being made under the
auspices of the Minister of Marine, and that these had proved that with
3 to 4 kilos of this new product it was possible for a man to live for
twenty-four hours in an hermetically closed chamber.
VISION WHEN SUBMERGED.
When completely submerged the submarine boat is practically blind, and
it is impossible to steer it by direct vision through the water. However
slow its course the steersman would be unable to stop it before an
obstacle which rose suddenly into the restricted circle of his aquatic
vision, and he is therefore obliged to steer his course by means of
bearings taken before descending.
At one time inventors believed that some light would come down through
the water to help the steersman, but it is now acknowledged that once
below the surface the boat is in impenetrable darkness. Some have
proposed the use of a powerful electric projector which would emit a
beam of light sufficient to light up a path 50 to 60 metres long in
front of the submarine.
Unfortunately such an arrangement is not possible in practice. In the
first place, such a projector would be of great size and weight and
would require a considerable amount of current, but even if it were
installed on a submarine it would be of no use to those on board for the
reason that they would be placed immediately behind it and would be able
to distinguish nothing owing to the great glare. The projector’s light
would also be likely to betray the position of the submarine owing to
the rays finding their way to the surface.
A submarine boat when navigating as an ordinary torpedo-boat on the
surface or in the “awash” condition can be steered from a cupola or
conning tower fitted with windows, which is affixed to the top of the
hull, and which remains above the water when the hull is below.
It was asserted that such a cupola would not only be of no use beneath
the waves, but would also be a disturbing element in the equilibrium of
the boat, reducing its speed. For this reason the _Gymnote_ and the
_Gustave Zédé_ were provided with telescopic domes capable of being
pushed up or down at will. The arrangement was very complicated, and did
not give good results, so it was abandoned, and all modern submarines
carry a fixed dome on their deck platform.
When the submarine is submerged to a depth not greater than 10 to 12
feet such aids to vision as the optical tube and the periscope may be
employed, but when the depth exceeds this limit the helmsman must rely
on his compass, coming from time to time to the surface to verify, and,
if necessary, rectify his route.
The periscope (from the Greek περι, around, and σκοπειν, look) is
applied to an instrument by which objects in a horizontal view may be
seen through a vertical tube. It may be said to consist of a vertical
tube with a lenticular total-reflection prism at the top by which
horizontal rays are projected downward through the tube and brought to a
focus, after which they are received by a lens, the principal focus of
which coincides with that point. The vertical cylindrical beam thus
formed is converted into a horizontal one again by a mirror inclined at
45° from the vertical axis of the tube, and is thus conveyed to an
eyepiece through which, by turning the tube on its vertical axis with
its attached prism, a view of all the supernatant objects around the
vessel may be obtained. A screen or diaphragm operated by a tangent
screw is used to cut off the view of the vertical plane in which the sun
is. When used on a submarine boat the top of the periscope floats on the
surface.
The optical tube with which the _Gustave Zédé_ was at first provided
before she carried a periscope consisted of a lens and a prism on the
top of a tube, and the image of the surface was thrown on to a surface
of paper. By the aid of the picture on the sheet of white paper the
steersman could, under certain circumstances, tell approximately where
he was going.
A writer in a recent number of the _Debats_ has something to say about
vision below water.
“We certainly possess these vessels capable of navigating under
water, which is no small advantage, but in order that they may be
able to fight under these conditions and become really effective
fighting machines the question of vision will have to be perfectly
solved. The _Moniteur de la Marine_ affirms that the periscope, the
apparatus intended to secure this power of vision, perfectly fulfils
its object. It gives, six metres under water, a good enough view of
what is going on upon the surface to enable a boat to steer towards
the enemy’s vessel without the necessity of rising to the surface to
make observations which quick-firing guns would render dangerous. No
less an assertion than this is necessary to shake certain doubts on
this point which will be shared by all who have been in a position
to observe the troubles caused to the vision by the water and vapour
on ground glasses. Only those who have used this instrument have the
right to say with Polycente, ‘Je vois, je sais, je crois, je suis
illuminé.’
“We who have not seen cannot go so far as this. It is also necessary
that the images given by the periscope should be susceptible of
rapid measurement, sufficiently accurate for the officer in command
to be able to know if he is near enough for his torpedo to prove
effective.
“In a word, the _Sous-Marin_ and the _Submersible_ are at present
marvels of applied mechanics. They will be fighting machines only
when the problems of vision and accurate measurement of distances
are fully solved. If this result is reached we shall not long be
kept in the dark, for with modern parliamentary methods all over the
world we shall witness the simultaneous appearance in all naval
budgets of demands for considerable sums in order to construct these
vessels.”
A device for submarine vision, termed the cleptoscope, and invented by
Messrs. Russo and Laurenti, is reported to be used on the Italian
submarine _Delfino_. In its original form the instrument, according to
the _Lega Navale_, gave an exact view in a closed chamber of all that
was to be seen round about a submarine to any one applying his eye to a
small eyepiece. In its later form it gives the same image much enlarged,
and visible to both eyes at once at some distance from the chamber.
As an illustration of the disadvantages arising from the fact that the
submarine is blind, the following story may be told, the accuracy of
which cannot however be vouched for.
An Italian submarine went out on one occasion for practice. All at once
the crew found that they could neither go ahead nor astern, nor could
they rise to the surface. They pumped out the spare water that was
provided to give additional buoyancy, but with no effect. The heavy lead
keel provided for an emergency was at last detached; still the boat
refused to rise, and the crew gave themselves up for lost.
The Port-guardship was riding in the anchorage, and fortunately her
captain heard a scraping and knocking which could not be accounted for
at the bottom of his ship. It occurred to him at last to signal to the
station on shore asking if the submarine boat was out for practice, and
on being told it was, he shifted his anchorage, whereupon the submarine
boat came to the surface with a rush like a cork, and the crew were
rescued in a very exhausted condition.
The optical instrument used on the new British submarines is termed the
“Hyphydroscope,” and is the invention of Sir Howard Grubb, F.R.S.