THE SUBMARINE OF TO-DAY
The feelings of the average landsman, when he sets foot for the
first time in a submarine, are a strong mixture of curiosity and
apprehension. The curiosity is uppermost--the experience before you
is much more novel than, for example, that of a first trip in an
aeroplane. From a mountain or tower, a great wheel or a balloon, you
have seen the bird’s-eye view of the earth and felt the sensation of
hanging over the aerial abyss. But even the fascinating pages of Jules
Verne have not told you all that you will feel in a submarine, and
nothing but physical experience can do so. You are eager to see the
working of new mechanical devices in a wholly strange element, and to
learn the use of a new weapon in a wholly strange kind of war. But
with this eagerness, there is an underlying sense of uneasiness, a
feeling that you are putting yourself into a position where you are as
helpless as a mouse in a patent trap. The cause of this is not fear of
war risks, for it is equally strong in harbour, or in time of peace. It
is probably connected with the common dread of suffocation, which may
be an instinct inherited from ages of primitive life in the open. They
will tell you, in the submarine service, that it is a mere habit of
mind and very soon forgotten. There is even a story of an officer who,
on coming ashore from a year’s work in an E-boat, refused to travel
in the Tube railway, because it looked so dangerous. He preferred the
risks he was used to, and so do most of us.
You stand, then, at the foot of the narrow iron ladder down which you
have come from the upper air, you gag your inherited instinct, and let
your curiosity loose. Before the boat dives, there is time for a good
deal to be taken in. The interior seems large beyond expectation. This
is partly an illusion, produced by the vista of the compartments, fore
and aft of the central control where you are standing. The bulkhead
doors being all open at this moment, you can see into the engine
and motor rooms towards the stern, and forward through the battery
compartment to the bow torpedo-tubes. The number of men seems large
too, and they are all busy; but you note that every part of them is
more active than their feet--there is very little coming and going. In
the control, close to you, are the captain, a lieutenant, a steersman,
and seven or eight other men for working the ballast tanks, air valves,
electrical apparatus, and hydroplanes. The last two of them have
just come down from the deck--the hatches are closed--engines have
already been running for some minutes, though the order escaped your
observation.
You are invited ‘to see her dive.’ You go up to the forward
conning-tower scuttle and flatten your face against the thick glass. An
order is given. You hear the hissing of air, as the ballast tanks are
filled. You expect to see the forward part of the boat dip down into
the water in which she is heaving. Instead of that, it is apparently
the sea which lifts itself up, moves along the deck, and seems to be
coming in a huge slow wave over your scuttle. The light of day gives
place to a green twilight, full of small bubbles. Mentally you feel a
slight chill; but physically, a warm and sticky sensation. As there is
nothing more to be seen out of window, you return to your instructor.
He explains to you that the ship is now running on her motors, and that
her speed is therefore low--not nearly enough to overhaul a vessel or
convoy of any power. On the surface, with her other engines, she could
far more than double the pace; and even with the motors, she could do
a spurt for a short time--but spurts are very expensive; for they use
up the battery power with ruinous rapidity, and then a return to the
surface will be necessary, whether safe or not.
At this point it may strike you suddenly that you are now under
water--you begin to wonder how deep you are, and why you have not
perceived any change in the boat’s position. The answer is that the
depth marked on the gauges is only twenty feet, and the angle of
descent was therefore very slight--much too slight to be perceptible
in the short length of a single compartment. The depth of twenty feet
is now being maintained with surprising steadiness; the explanation is
that two entirely separate forces are at work. First, there are the
horizontal rudders or hydroplanes, fitted outside the vessel both fore
and aft, by which she can be forced down, provided she has sufficient
way on, in much the same fashion as an ordinary vertical rudder forces
a ship to one side or the other. But this is only the diving apparatus;
to keep her down, there is her water ballast--the water which was taken
into her main ballast tanks, when the order to submerge was given.
These tanks contain a sufficient weight of water to counteract the
normal buoyancy of the boat, by which she would naturally float upon
the surface. When they are emptied, she will neither sink nor rise of
her own motion--she will lie or run at whatever depth she is placed, by
her hydroplanes or otherwise.
These, you will have noticed, were called the ‘main’ ballast
tanks--there would seem then to be others. There are, and several
kinds of them. First, there is an auxiliary ballast tank, which has a
peculiar use of its own. A submarine must be able to float or submerge
in fresh water as well as at sea; for her base or harbour will often
be in the mouth of a river, or she may have to navigate a river, a
canal, or a lake. It is a point that would not probably have occurred
to you, but the difference between the density of fresh and salt water
is sufficiently great to make a real difficulty here. Everyone knows
that it is less easy to float in fresh water, and less easy to sink in
salt. For practical purposes, a submerged boat is less buoyant in fresh
water by 26 tons in 1000, and _vice versa_; so that when a submarine of
1000 tons leaves a river for the sea, she must take an extra 26 tons of
ballast to keep her down, and when she comes home again she must get
rid of 26 tons, or she will sink so much deeper in the fresh water. For
this purpose she has a special tank of the right size, proportioned to
her tonnage; and it is placed in the middle of the ship, in order that
it may not interfere with her trim when it is filled or emptied.
That last remark will put you in mind that, in any kind of navigation,
the trim of the boat is a delicate and important matter. Even in very
large and heavy ships you may be able, by shifting guns or cargo, to
slip off a shoal, or right a leaking vessel after a collision. In a
tickle boat like a submarine, it is necessary to have some means of
trimming the vessel, fore or aft, at any moment, and especially when
about to dive, or when caught by some under-water obstruction. Tanks
are therefore fitted for this purpose at each end of the boat. They
are comparatively small, because the effect required is in ordinary
circumstances very limited, and in a desperate emergency they may need
to be supplemented by rushing the crew fore or aft, as living ballast.
An example of this will be found in a later chapter.
You may now feel that you have heard enough of tanks; but your
instructor will insist on showing you a whole additional series. He
will make a point of your recognising that a submarine, when submerged,
is in reality hanging in the water as a balloon hangs in the air, and
for every loss of weight she must be instantaneously compensated,
or she will begin to rise. What loss of weight can she suffer while
actually under water? It is not perhaps very hard to guess. There is,
first of all, the consumption of oil by the engines; secondly, the
consumption of food and fresh water by the crew; and thirdly, the
departure from time to time of torpedoes. Also, when on the surface,
there may be gun ammunition fired away, or other things heaved
overboard, and allowance must be made for this when the boat goes down
again. The modern submarine is prepared to keep her balance under all
such circumstances. She has compensating tanks, and they are placed as
near as possible to the oil-tank, fresh-water tank, or torpedo-tube,
for whose diminished weight they are to compensate.
You are probably more interested in the torpedo-tubes than in the
oil-tanks. It is time then to go forward. You pass through the battery
compartment, where the officers’ quarters are, and are shown (under the
floor) the accumulators, ranged like the honey sections in the frames
of a beehive, and very carefully covered over with flexible waterproof
covering as well as with close-jointed planking. What would happen if
water did find its way down to the batteries? An instant discharge of
chlorine gas, blinding and suffocating. What would you do then? Come
to the surface at all costs--and lucky if you are in time! The Germans
know all about that--and not long ago one of our own boats was only
saved by the good goal-keeping of a lieutenant, who caught up a lid of
some sort, and stood by the leak, neatly fending off the water spurt
from the door of the battery compartment.
Now you are in the forward torpedo compartment, and there are the
tubes. I need not say anything about their size or number--you will
realise at a glance that when a couple are loosed off at once, a good
deal of weight goes out of the ship. The ordinary 18-inch fish is 17
feet long, and takes some handling. The explosive alone in her war-head
weighs as much as a big man, say 12½ stone, and a 21-inch fish carries
twice as much as that, packed in some four feet of her length. Behind
that comes the air chamber--another ten feet--with the compressed air
to drive the engine, which is in her stern. The air is stored at a
pressure of over 2000 lbs. to the square inch; so the steel walls of
the chamber must be thick, and this makes another heavy item. Lastly,
there is the engine-box with its four-cylinder engine, two propellers,
gyroscope and steering gear. Altogether, an 18-inch fish will weigh
nearly three-quarters of a ton, and a 21-inch over 2000 lbs., so that
the amount of compensation needed when you fire, is considerable.
To see how it is done, we will imagine ourselves firing this starboard
tube. The torpedo is got ready, and special care is taken to make
sure that the firing-pin in her nose is not forgotten. Cases have
been known in which a ship has been hit full by a torpedo which did
not explode--just as a good many Zeppelin bombs were found in London,
after the early raids, with the detonating pin not drawn. The fish is
now ready to come alive, and is slid into the tube. The door is shut
behind it, and the water-tight outer door, at the other end of the
tube, is now ready to be opened by powerful levers. But the immediate
result of this opening would be an inrush of sea-water which would
weigh the boat’s head down; for though the fish’s belly fits the tube
pretty closely, there is a good deal of empty space where it tapers
towards the nose and tail. Here comes in the tank system. When the tube
is loaded, this empty space is filled by water from within the ship,
so that no change of weight occurs when you open the outer door. But
when the firing-button has been pushed, and the torpedo has been shot
out by an air-charge behind it there is no possibility of preventing
the whole tube from filling with water, and this water must be got rid
of before the tube can be reloaded. To do this, you first close the
outer door again; then you have to deal with the tubeful of water. A
good part of it is what the ship herself supplied to fill the space
round the torpedo; and this must be pumped back into the special tank
it came from. The remainder is the sea-water which rushed in, to take
the place left empty by the departing torpedo: and this must be pumped
into another special tank to prevent the ship feeling the loss of the
torpedo’s weight. When you get a fresh supply of torpedoes, these
special compensating tanks (which are really a kind of dummy torpedoes)
will be emptied out, one for each new torpedo. Meantime, you have now
got the tube empty, and can open the inner door and reload.
But what of the torpedo which has been fired? It is travelling towards
its mark at a speed of between thirty-five and forty knots, if we
suppose the range to be an ordinary one, under 1000 yards, and the
torpedo to have been ‘run hot,’ _i.e._ driven by hot air instead of
cold. The compressed air is heated mechanically inside the torpedo,
in the act of passing from the air chamber to the machinery, and this
increases both the speed and range. But it is not always convenient or
possible to start the heating apparatus, and even when ‘run cold’ the
fish will do thirty knots. This speed is amazing, but it is one of the
least wonderful of the torpedo’s qualities. The steering of the machine
is a double miracle. One device makes it take, after the first plunge,
exactly the depth you desire, and another--a gyroscope fitted inside
the rudder gear--keeps it straight on its course; or makes it, if you
wish, turn in a circle and strike its prey, boomerang fashion. The head
of the fish can also be fitted with cutters which will cut through any
torpedo-netting that a ship can afford to carry. The only thing that no
ingenuity can accomplish is to make a torpedo invisible during its run.
The compressed air, when it has passed through the engine, must escape,
and it comes to the surface in a continuous boiling line of bubbles.
This is visible at a considerable distance; and though, when the track
is sighted by the look-out, the torpedo itself is of course always
well ahead of the nearest spot where the bubbles are seen rising, it
is surprising how often ships do succeed in avoiding a direct shot. A
prompt cry from the look-out, a steersman ready to put his helm over
instantly, and the torpedo goes bubbling past, a few feet ahead or
astern, or comes in on a tangent and runs harmlessly along the ship’s
side without exploding. Then away it goes across the open sea, until
the compressed air is exhausted, the engine stops, and the mechanical
sinker sends it to the ocean bed, which must be fairly strewn with
dead torpedoes by this time; for as we know, to our advantage, the
proportion of misses to hits is very large in the U-boat’s record.
Now that you have seen the weapon--and can at any rate imagine the
handling of it--you are naturally keen to sight the game, and realise
the conditions of a good shot. You go back to the central compartment,
where the Commander is ready to show you a ship through the periscope.
Not, of course, an enemy ship--in this war, if you want a shot at an
enemy ship, you must go into his own waters--into the Bight or the
Baltic--to find him; and even there he is probably tucked up very tight
in his berth, with chained barges and heavy nets all round him, and
mines all up the approach. But there are plenty of our own ships out
every day--sweeping, cruising, trading; and transporting men, food,
mails, and munitions. And what you see will help you to understand why
the Germans have spent so many torpedoes, and sunk so comparatively
small a proportion of our enormous tonnage.
The boat is now less deep in the water; the gauges mark 15 feet, and
you are told that the top of the periscope is therefore some two feet
above the surface. The shaft of it is round, like a large vertical
piston; but at the bottom it ends in a flattened box, with a hand-grip
projecting on each side. You take hold of the grips and look into the
box. Nothing is visible but an expanse of water, with a coast-line
of low hills beyond it--all in miniature. The Commander presses the
back of your left hand on the grip, and you move round slowly as the
periscope revolves. The coast-line goes out of the picture, the sea
lies open to the horizon, and upon it appears a line of odd-looking
spots. They are moving; for the nearest one, which was narrow a moment
ago, is now three or four times as broad, and is in a different place
in the line.
The line, you are told, is not a line at all, but a convoy, in fairly
regular formation. The nearest spot is a destroyer, zigzagging on the
flank; the others are ships which have been so effectively ‘dazzled’
that their shapes are unrecognisable. You carry on, in hope of
something nearer, and suddenly a much larger object comes into the
field of vision. A ship, of course, though it does not look like any
ship you have ever seen; and you are asked to guess its distance and
direction. You are bewildered at first; for as you were moving the
lens rapidly to starboard, the vessel came in rapidly to port, and
as her dazzle-paint makes her stern indistinguishable from her bows,
you continue to think she is steaming in that direction. After a more
careful observation, this mistake is corrected. She is crossing us from
port to starboard. But at what angle? This is vitally important, for
the possibility of getting in a successful shot would depend entirely
upon the answer. We are ourselves heading about due north: she is
crossing to the east: if her course is south of east, she is coming
nearer to us, and our torpedo would strike her before the beam--the
most favourable chance. If, on the contrary, her course is north of
east she is going away, and the torpedo would have a poor chance of
hitting her abaft the beam. In fact, it would not be worth while to
risk losing so costly a shot. A torpedo at present prices is worth not
far short of £2000, and we only carry two for each tube.
You look long and hard at this dazzle-ship. She doesn’t give you
any sensation of being dazzled; but she is, in some queer way, all
wrong--her proportions are wrong, she is somehow not herself, not
what she ought to be. If you fix your attention on one end of her,
she seems to point one way--if you look away at her other end, she is
doing something different. You can’t see the height of her funnels
clearly, or their relative position. But, with care, you decide that
she is coming about south-east and will be therefore your bird in two
minutes’ time. The Commander is interested. He takes a look himself,
laughs, and puts you back at the eye-piece. You hold on in hope that he
may, after all, be wrong; but the bird ends by getting well away to the
north-east. Your error covered just ninety degrees, and the camouflage
had beaten you completely. You begin to think that the ingenuity
at command of the nation has been underestimated. But this ship is
nothing of a dazzle, the Commander tells you--he can show you one whose
cut-water seems always to be moving at a right angle to her stern!
[Illustration: ‘Does not look like any ship you have ever seen.’]
He adds that he knew all about that cruiser, and she knew all about
him. Otherwise he would not have shown even his periscope; and if he
had, she would have had a shell into him by now, and a depth-charge to
follow. A depth-charge is perhaps the most formidable weapon against
which the submarine has to be on guard. It is a bomb, with a detonator
which can be set to explode when it reaches any given depth. A small
one would need to hit the mark full, or be very close to it, in order
to get a satisfactory result; but the newer and larger ones will
seriously damage a submarine within an area of forty yards. The charge
is either dropped over the stern of the pursuing vessel, when she is
thought to be just over or just ahead of the enemy; or it is fired out
of a small and handy short-range howitzer--a kind of lob-shot, a number
of which can be made by several patrol boats acting together, so as to
cover a larger area with much less risk of embarrassing each other.
Even if the submarine is not destroyed outright, the chances are in
such a case that she will be so damaged as to be forced to the surface
or to the bottom, and then the end is certain. A bad leak would bring
her up--an injury to her tanks or rudders might drive her down.
You are uncomfortably reminded once more of that inherited dislike of
death by suffocation. If a submarine cannot rise to the surface, you
ask, is there no possible means of escape? The answer is that it may be
possible, with great difficulty, to get out of the boat; but there is
very little chance that you would survive. The lungs are not fitted to
bear so great and sudden a change of pressure as that felt in passing
from the boat to the water, and from the deep water to the surface.
You are perhaps surprised; but the pressure of sea-water at 160 feet
is equal to five atmospheres, or about 75 lbs. to the square inch. To
pass safely through this to the ordinary surface atmosphere would need
a long and gradual process, and not a sudden rise of a few seconds. A
very brave attempt was made on one occasion, when a British submarine
had gone to the bottom during her trials, and could not be got up by
any effort of her crew. The agony of the situation was intensified by
the fact that help was close at hand, if only the alarm could be given,
and the whereabouts of the submarine communicated to the rescuers. The
officers of the sunken boat were, of course, perfectly aware of the
danger from sudden change of pressure; but one of them volunteered to
go to the surface, alive or dead, and carry a message on the chance
of attracting some ship’s attention. To lessen the risk as far as
possible, it was arranged that he should go up into the conning-tower,
and that the hatch should then be closed beneath him and the water
gradually admitted. As it flowed slowly in, and mounted round him,
the air in the top of the conning-tower would diminish in extent but
increase in pressure. When it reached his neck, the internal pressure
would be nearly equal to the external. He would be able to open the
top, possibly to make his escape, and conceivably to reach the surface
without his lungs being fatally injured. If he failed, he would at any
rate have given his life for the chance of saving his comrades.
The Commander accompanied him into the conning-tower, meaning, it is
said, to return into the ship himself when he had seen to all the
arrangements. But when the water was admitted, the two of them were
shot out together, and as it happened it was the volunteer who was
killed, by striking against the superstructure, while the Commander
came up alive. In no long time--though it must have seemed unendurably
long to those below, waiting in complete uncertainty--the rescuers were
informed, found the submarine, and got a hawser under her stern. They
raised her high enough out of the water, vertically, to open a hatch
and save the crew. Then the hawser gave, and the boat went down again.
That story is not unlikely to haunt you all the way home, and for a
long time afterwards. It may even make a difference to your whole
feeling about the war under water, as waged by our own Service. The
submarine is not merely an incredibly clever box of mechanical toys,
nor is it only the fit weapon of a cruel and ruthless enemy; it is
also a true part of the Navy without fear and without reproach, whose
men play the great game for each other and for their country, and play
it more greatly than we know. The tune of their service is a kind of
undertone; but it is in the heroic key, and cannot fall below it.