THE POSSIBILITY OF DEFEATING THE SUBMARINE
In the present European war, for the first time in the world's history,
the submarine, as is also the case with the airplane, has taken an
important active part, and has become a weapon of unlimited value. We
have seen that even as early as the war of the American Revolution the
submarine was utilized, but up to modern days the submarine had never
been a really significant or consequential factor in naval warfare;
its use had been previously but sporadic and experimental. In the wars
of the past it had no bearing upon the destinies of nations or the
outcome of naval battles. To-day the situation is very different: the
submarine has been called into action as a weapon of primary value and
is producing tremendous results.
In the conflict in which we are now engaged the destructive
capabilities of the submarine have been made use of, for the most
part, in the work of commerce destruction and in the task of hampering
communication by sea. It has not taken a great deal of active part
in actual naval battles, although on some occasions its presence has
been severely felt by the fleets of its enemies. But the submarine
has been an important factor in naval warfare by reason of the fact
that its very presence and the possibility of its use have checked the
actions of belligerent fleets of battleships in no inconsiderable way.
In writing of this I am reminded of the fact that a short time ago I
was introduced to a pleasant-faced, motherly old lady who, when she
learned that I was an inventor of submarine boats, exclaimed, "Why! I
should not think you could sleep nights from thinking of all those poor
people who have been drowned by the U-boats!"
I asked the old lady if she had ever considered the submarine from
another angle of view--viz., as a life and property saver in the
present war--and she said, "No; how could that be possible?" I then
explained to her that had it not been for the existence of the
submarines many more lives would have been sacrificed than have been
lost by the use of submarines. I asked her to consider what would
have been the loss of life if the battleships, cruisers, gunboats,
destroyers, etc., had met on the high seas and fought as they were
intended to fight. A submarine carries a crew of but a few men, while
a battleship may carry a thousand, consequently thousands of men would
have been killed in the old-time methods of fighting, compared with the
few that have been killed in the submarine warfare. Then again, had it
not been for the submarines lying off Russia's, Germany's, England's,
France's, Italy's, Austria's, and even Turkey's shores, many seacoast
cities, towns, and hamlets would undoubtedly have been bombarded and
destroyed, and countless thousands of lives and enormous property
valuations lost forever to the world; for one must remember that a
life, or a property once erected by hands that are gone, if lost, can
never be economically replaced. The only reason such bombardments have
not occurred is the fleet commander's fear of that waiting, watching
invisible sentinel, the submarine, which lies off the respective
combatants' shores; and thus because of its existence thousands of
lives and great property valuations have been saved. Thus, while the
submarine has not been much of a fighter in naval battles, it has, in
my opinion, been of great power as a preventer of fighting, and that,
after all, is rather more in its favor than against it.
It is, however, the submarine in the role of commerce destroyer which
is attracting attention at the present time. The democratic nations
of the world are face to face with the problem of transporting men,
food, ammunition, and supplies to Europe. The submarine threatens to
cut off communication between Europe and the other continents. It is
very necessary that means be taken to offset the activities of the
submarine. It is this problem which leads me to write upon this topic.
[Illustration: BRITISH SUBMARINE C-2 ARRIVING AT PORTSMOUTH IN A GALE
Note hydroplanes at centre of conning tower; in later types these
were placed under the water, as they were found ineffective in this
position]
The devices which have been proposed for capturing and destroying the
U-boats in order that navigation upon the Atlantic Ocean may be made
safe have run into the thousands. I have had hundreds of impractical
schemes sent to me, and the Navy Department and the Naval Consulting
Board have been almost swamped by the various suggestions that have
been pouring in from all over the country in response to editorials
in the newspapers to "Save us from the U-boat!"; "American inventors,
rise in your might and strike down this peril which works unseen, like
an assassin in the dark!" etc. The devices proposed run all the way
from blowing up the whole restricted area or war zone of the ocean to
fishing for submarines from aeroplanes, which latter method offers a
good chance for sport, at least; and if the submarine designers and
commanders were asleep the fishermen might have a good chance of making
a catch. Many of my engineering friends with whom I have discussed
the U-boat problem have urged upon me that I ought, in order to
save the time, energy, and money of many earnest and patriotic--but
misinformed--citizens, to publish some material showing the fallacies
in many of these schemes which apparently are so promising, and at the
same time to point out wherein some have value, and along what lines I
believe success to be attainable.
At the beginning of the war I myself sent to the Navy Department
a number of devices for detecting the presence of and destroying
submarines in shoal waters, some of which may have already been
known to the Navy Department, and several of which I have since seen
published as being the ideas of others; this goes to show that where
many minds are working toward the solution of any particular problem
several are likely to arrive at the same point. In the interest of
public policy I do not think that any device hitherto unknown which
offers a chance of success if used against an enemy U-boat should be
described, and therefore I should not describe any such device if such
were known, but shall limit my remarks to a discussion of some of the
devices that have been proposed and described publicly. Trying to serve
the country by developing a certain idea, when that idea is itself
old or impractical, is evidently a waste of mental energy and money.
Further, to show how some of these methods of attack may be offset by
the submarine commanders will also serve to prevent the country from
relying on false defences; the submarine is a real menace, and should
not be lightly regarded. I hope to impress upon people that this is a
very serious proposition. It is a problem which should and does attract
the leading minds of the mechanical world; and it is not to be coped
with by any fanciful notions. While the devices proposed thus far are
individually very numerous, they may be classified into a few distinct
categories. I would designate them as follows:
_Offensive Devices:_
I. Airplanes and dirigibles for the location and destruction
of submarines.
(_a_) By bomb attacks.
(_b_) By directing surface boats to the attack of
sub-vessels.
II. Offensive appliances for use of surface vessels:
Sound detectors.
Submerged mines operated from shore stations.
Deck guns.
Under-water guns.
Aerial torpedoes.
Searchlights.
Echo devices.
Magnetic devices for locating and destroying submarines.
III. Channel and open-sea nets.
IV. Submarine vs. submarine.
_Defensive Devices:_
I. To be installed on surface vessels to baffle and elude submarines:
Sound detectors (spoken of above).
Blinding searchlights.
Blinding apparatus.
II. To offset torpedo attack:
Nets.
Plates.
Magnets.
Bombs.
Discs.
III. Unsinkable ships.
IV. Tactics to elude the submarine:
Convoying a merchant fleet.
Zigzag course.
Smoke screen.
Cargo submarine.
High speed.
In considering the practicability or value of these devices, we must
first consider the capabilities of the submarine and the proper tactics
for her commander to pursue. In a paper read before the Institution
of Naval Architects in London, in 1905, I described, illustrated by
diagrams, the proper method to be pursued in attacking a surface ship,
in which I contended that the commander of a submarine, on sighting an
enemy, should always keep the hull of his own boat below the horizon in
its relation to the enemy vessel, and try to intercept the approaching
vessel by taking frequent observations of her course and speed. When
the two vessels approach sufficiently near to make it possible for the
larger surface vessel to observe the smaller submarine (the comparative
range of visibility being proportionate to the exposed surfaces of the
two vessels above the horizon), the submarine should then entirely
submerge, with her telescopic periscope withdrawn below the surface of
the water to avoid the making of a "wake"--which looks like a white
streak on the water. When the commander wishes to make an observation
he should first bring his submarine to rest and then extend the
periscope above the surface for a brief instant only, and thus avoid
the chance of being seen. Earlier in the war it was common to detect
the submarine by her wake, but now, since the fitting of merchantmen
with guns, the above tactics are usually pursued, and the first
intimation the crew has of the presence of the submarine is the shock
of the explosion caused by the torpedo "striking home."
[Illustration: GERMANY'S U-9 AND SOME OF HER SISTER SUBMARINES]
[Illustration: AEROPLANE AND SUBMARINE
(Drawing by T. E. Lake.)
For defense of coast lines aeroplanes and submarines may work in
conjunction. Aeroplanes, with their enormous range and high speed can
locate surface ships many miles away, beyond the range of a submarine's
periscope or sound-detecting devices. It could then direct the
submarine by wireless or direct communication. Aeroplanes, however, are
of great danger to enemy submarines. Flying at certain altitudes they
can see submarines a short distance below the water and swoop down on
them, dropping depth bombs or trailing torpedoes.]
=Aeroplanes and Dirigibles.=--These are undoubtedly valuable near land
in shallow water, _providing_ the water is clear and has a bottom in
striking contrast to the hull of the submarine. I should consider
the dirigible likely to prove of more value than the aeroplane,
owing to its ability to hover directly over and regulate its speed
to that of the submarine and thus enable itself to drop depth bombs
more accurately. Experience has shown that it is almost impossible to
calculate where a bomb will strike when dropped from a swiftly moving
aeroplane. The chance of its striking the submarine would be very
slight. The use of aeroplanes has, however, forced the submarines away
from shoal clear water and probably has been instrumental, also, in
causing them to become equipped with high-angle rapid-firing guns.
In a battle between swiftly moving aeroplanes and submarines with
high-powered guns firing shrapnel, the chances are nearly all in favor
of the submarine, as they can carry the most powerful guns and are
firing from a much more stable platform; in fact, the best analogy
I can think of is that of a gunner in a "blind" firing at a flock
of ducks passing overhead. Aeroplanes have been used, however, as
scouts, merely to detect a submarine and direct surface ships to the
attack; also, aeroplanes have directed trawlers to a submarine lying
submerged at a shallow depth. This method of attack has undoubtedly
been successful in some instances, but where success might have been
met with in this manner with the earlier submarine boats, which were
not provided with guns, it is now a problem easily met by submarine
architects. Submarine boats may be built which have no fear of this
combination. One of my earliest designs provided for a revolving
armored turret to carry heavy-calibre guns; this revolvable armored
turret would extend only above the surface and would carry guns of
sufficient calibre to sink any trawler, destroyer, or other craft
except an armored ship. It has recently been reported that the Germans
are bringing out ships fitted with turrets of this type, and as they
are familiar with my designs from the Patent Office specifications,
and also have my working drawings of a large cruiser submarine mounted
with guns, in 1905, I have no doubt that the report is true, as they
have consistently been the first to adopt such new devices as may be
needed to offset any attack against their submarines, or to increase
their means of offence against surface craft without relying upon
torpedoes alone. As far back as 1902 the _Protector_ was fitted with a
small gun on top of her conning tower, with the breech extended into
the sighting hood and a tampon controlled from within the turret for
closing the muzzle, so that no water would enter the barrel when the
vessel was submerged, thus permitting a new cartridge and shell to be
inserted into the breech when submerged; then, by momentarily bringing
the conning tower above the surface, we could fire, then submerge and
reload, rest and fire again, etc., thus providing a disappearing gun on
a very stable platform.
In deep water the submarine may readily escape detection by aeroplanes
by sinking below the depth to which vision can penetrate. This depends
upon the amount of foreign substance held in suspension in the water.
Along the Atlantic coast it is possible to see only a few feet; as you
go off shore vision becomes clearer, and it would probably vary during
the dry seasons from four to five feet near shore to forty or fifty
feet well off shore. The greatest distance I was ever able to see in
my experiments in the Chesapeake Bay with a powerful searchlight was
forty feet. In Long Island Sound one can seldom see over fifteen feet,
and after storms, when sediment is carried into the Sound, sometimes
it is difficult to see over three or four feet. I have been down on
muddy bottom at a depth of one hundred feet and could not see my hand
held close to my face. At a depth of one hundred and twenty-five feet
in the Baltic on sandy bottom I was able to see twenty-five feet.
This was about eight miles off shore, opposite Libau, Russia. In the
English Channel the frequent storms stir up so much sediment that it is
seldom possible to see over fifteen feet, while in the Mediterranean
and our Southern waters near the Florida coast, near Nassau, and in
the Caribbean Sea, it is possible at times to see seventy-five or even
one hundred feet. Now there are means available to the submarine to
enable it to lie at rest submerged at depths exceeding one hundred
feet, and yet have a full view of surface ships and also to scan
the heavens, therefore I would say that aeroplanes and dirigibles
will prove ineffective against submarines fitted with revolvable
turrets, high-angle firing guns, or where they may be operating in
clear water exceeding one hundred feet in depth or in shallow water
where the sediment held in suspension is in sufficient quantity to
prevent discovery. Aviators with whom I have discussed this problem
tell me they can seldom detect objects lying on the bottom, even in
comparatively shallow water.
[Illustration: RUSSIAN CRUISER-LAKE TYPE SUBMARINE IN SHED BUILT BY
PETER THE GREAT--1905
This was the first large submarine of the cruiser type, built
substantially after the design submitted by the author to the U. S.
Navy in 1901.]
=Sound Detectors.=--We have heard many claims put forth concerning the
great results which were to be attained in fighting the U-boat by the
use of various sound-receiving devices in the nature of microphones, in
detecting the presence of submarines by hearing the hum of the motors
and the noise of their machinery. These devices are proposed both for
offensive and defensive purposes. A vessel equipped with such mechanism
is believed to be able to escape upon hearing a U-boat, or to seek out
the submarine and destroy it. Those who have been expecting so much
from this source are probably not aware of the fact that submarine
inventors themselves were the first to utilize this method of sound
detection under water to enable them to apprehend the presence of other
vessels in their vicinity before coming to the surface; they have made
use of such devices for years.
I well remember my first long submergence of ten hours' duration down
at Hampton Roads, near the mouth of the Chesapeake Bay, July 28, 1898.
During this period of submergence the machinery was shut down for a
time, and one of the first sensations we experienced was the strange
sounds which came to us of the propellers and paddle-wheels of surface
vessels passing in our vicinity. The first vessel that we heard was a
tugboat; we could tell that by the sound of her puffing exhaust and
the characteristic sound of her machinery. We thought at first she was
coming right over where we were submerged, and feared she might carry
away our masts, which extended above the surface, but she passed on,
and then we heard coming at a distance the uneven and characteristic
sound of a paddle-wheel steamer as her paddles slapped the surface of
the water. Then we heard the slow, heavy pound of an ocean liner coming
in, and knew that she had a loose crank-pin or cross-head bearing by
the pound every time the crank-pin passed over the dead centre of its
shaft. The click, click of the little high-speed launch was also easily
detected--all this without any sound receiver on the vessel. Any of
us simply sitting or standing anywhere in the submarine could hear
outside sounds. By putting the head of an iron bolt against the skin
of the ship and sticking the end of the bolt in my ear the sound was
much intensified, as the whole steel fabric of the ship became a great
sound collector. This led me to make experiments toward determining
the direction of the sounds under water, and I applied for a patent on
a device which could be swung in different directions, on the theory
that the sound waves would be stronger when coming straight from their
source, but shortly after this the experiments of Professor Gray and
Messrs. Munday and Millett were published and I dropped my application
and did nothing further in the matter, as they seemed to have solved
the question in a satisfactory manner. Afterward Professor Fessenden
brought out his oscillator and improved sound detector, with which it
is possible for submarines to carry on wireless conversations under
water when at a distance of several hundred feet apart, and to pick
up the characteristic sounds of different types of surface ships at
considerable distances. Sound detectors are of greater benefit to
submarines lying in wait for their enemies than they are to surface
vessels, as they enable the submarine to lie at rest, submerged and
invisible, herself giving no betraying sound, while no surface ship
can come within the zone of her receiving apparatus without betraying
its presence.
=Submerged Sound Detectors.=--It has been stated that sound detectors
connected to shore stations have been able to detect submarines
when passing in their vicinity, and, by the triangulation method as
applied to the intensity of sounds, observers have been able to tell
approximately the location of the U-boat from the sound of the U-boat's
machinery. The obvious thing for submarine designers and commanders to
do to offset this danger to the submarine is to use noiseless machinery
in the U-boats, or to send other U-boats with a wire-cutting grapnel to
cut the shore connections of the sound transmitter. It is apparent that
this method of attack is applicable only to points close to shore or in
places like the English Channel.
[Illustration: A GROUP OF GERMAN U-BOATS
Note their broad decks, due to buoyant superstructure.]
[Illustration: RUSSIAN-LAKE TYPE CRUISING SUBMARINE "KAIMAN" MAKING A
SURFACE RUN IN ROUGH WEATHER IN THE GULF OF FINLAND]
=Deck Guns.=--The mounting of deck guns on merchantmen for defence
against the submarine has proved of slight value. When it was first
proposed to mount guns on American merchant ships I wrote the Navy
Department on March 11, 1917, in part as follows: "I have tried, in
the interest of this country, to impress this fact upon the people
(that the submarine, because it is invisible, is invincible), but
I find in talking with many intelligent people, that they do not
and cannot comprehend the possibilities of the submarine when it is
taken seriously and the effort is made to get all there is out of it,
without reference to political, financial, or prejudiced interests.
The _destructiveness_ of the submarine is growing; devices which were
effective in detecting and trapping submarines early in the war are
now becoming useless. The theory that putting a gun on a merchant ship
is going to protect that ship, her crew and passengers, will, I fear,
be equal to the signing of the death-warrant of all that are on that
ship if we are at war, as the slogan in to-day's headlines (as per copy
clipping enclosed)--'Sink any ship you see'--will be met, I fear, by
a German slogan of 'Sink every ship you meet, but don't let them _see
you_ do it.'"
Since that time many ships fully equipped with arms have been sunk by
torpedoes and have never seen the submarines which destroyed them.
There is no way to attack submarines by gun fire unless they are seen,
and commanders of submarines are becoming expert in concealing their
presence.
=Submarine Guns, Aerial Torpedoes, Searchlights.=--For an under-water
gun to be effective, there must first be discovered some way to locate
the target; this, of course, is almost impossible. Aerial torpedoes or
depth bombs might be effective if the submarine were seen, but it is
the business of the submarine commander to keep out of sight. Powerful
searchlights have very little chance of picking up the periscope or
conning tower of a submarine. I remember lying all one night in the
_Argonaut_, during a storm, at the outer edge of the mine fields off
Fortress Monroe, at the time the whole country was in dread of an
invasion by Cervera's fleet during the Spanish-American War. We were in
forbidden territory, having been delayed by the storm in getting into
harbor before "Curfew" rang, so to speak. The powerful searchlights of
Fortress Monroe were playing all night, but they did not detect our
presence, as only our sighting hood was above water, and presented such
a small object, and being painted white, it was not distinguished from
the "white caps" on top of the sea caused by the storm.
Searchlights under water are useless because of the particles of
foreign matter held in suspension which reflect back the glare of
the light. The _Argonaut_ was fitted with powerful searchlights and
reflectors located in her extreme bow, with a pilot-house or lookout
just above the three searchlight windows. The greatest distance we were
ever able to see was during some night experiments in the Chesapeake
Bay during a long dry spell, when the sediment had had an opportunity
to settle, and that was only forty feet. The light would penetrate
through the water several hundred feet and make a glow on the surface,
but vision could not penetrate the water. For instance, it is said that
after a storm a glass of Mississippi River water will show fully an
inch of sediment. To see through three or four inches of that kind of
water, therefore, one must see through an inch of mud. It is well known
that no light has yet been found that will enable vision to penetrate
through a heavy fog, due to the reflection of light upon the minute
crystals of water held in suspension in the air. It appears hopeless,
therefore, to expect vision to locate submarines by seeing through the
opaque substance held in suspension in all water.
=Echo and Magnetic Devices.=--Locating submarines by echo has been
proposed, but apparently without thought as to what would happen to
the vessel giving out the sound in the effort to get an echo back
from a submerged submarine, lying in wait with her "ears" waiting to
hear some suspicious sound. Also, magnetic devices for the purpose of
detecting submarines, if ever found practical, will probably be kept
so busy leading their operators to and investigating large steel ships
that have already been sunk by submarines that they will probably
miss the little submarine, which can easily sink them while they are
investigating these other sunken ships.
=Channel and Open-sea Nets.=--These have been and are being used with
some success, but that success has been attained only because at the
beginning of the war the submarines had no means for determining the
presence of the nets before becoming entangled in their meshes, and
when they once became entangled they had no means to cut themselves
loose. Devices are now available which enable the commander of a
submarine to locate a net before reaching it, and to destroy that net
and all its attached mines with but little danger to his own vessel. To
what extent these devices are being used is unknown. However, when the
submarine is not especially fitted for the detection and destruction of
nets and attached mines, they are probably the most efficient type of
trap yet provided for capturing and destroying these "submarine devil
fish." The _Scientific American_ published an article by me in 1915
describing a submarine fitted with mine-evading devices and meant to
under-run nets, which has been reproduced in the previous chapter.
[Illustration: THE U-65
Photograph copyright by Underwood & Underwood
One of the large German U-boats fitted with deck guns hailing a Spanish
merchantman which they have held up.]
[Illustration: RUSSIAN-LAKE TYPE
These vessels are powerfully armed, fitted with four torpedo tubes
firing fore and aft, also Dzrewiecke apparatus for firing torpedoes to
either broadside.]
The above articles having been published previous to our country
entering the war, and being thus of public knowledge, it is permissible
to republish them as a method which might be used to advantage in
preventing the German submarines from coming out from their bases. It
is admitted that the allied fleets are overwhelmingly superior to the
German fleet, yet they are impotent to attack the German battle fleet
or to make reprisals on Germany for the constant depletion of their
merchant fleet, because Germany's fleet of battleships, cruisers, and
merchantmen will not come out in the open, but lies safe behind nets
and mine fields as their inner defence, using her submarines on her
outer line of defence. As mentioned, Winston Churchill said we must
"dig them out like rats out of a hole." That was over three years ago,
but not one has been dug out as yet, and, although it would be a very
expensive process to do so, it might be possible, by the coöperation of
submarines, surface ships, trawlers, and aeroplanes, to move forward
gradually and expansively a double or treble line of nets and to defend
such a line of nets just outside of the range of the most powerful
shore-defence guns. The battleships should be protected by operating
between the line of nets to prevent attack upon them by submarines in
the rear. Bottom-working submarines would be needed to clear away the
mines and nets of the enemy as the mines and nets were moved forward.
Constant patrol and repair of the nets would be maintained under the
guns of the net-protected fleet, and allied submarines must be on
constant attendance in advance of the first line of nets to meet the
concerted attack of a portion of the German fleet in "rushing" the
line--which must be expected in the attempt to break the same--in order
to let out a fleet of their submarines into the open sea to continue
their attacks on the allied and neutral commerce of the world. This
seems to me the only practical way of stopping up the hole or holes
through which the German submarines come out, and to make it effective
it would require a double line of nets and patrol fleets extending
from Norway to Scotland, and across the English Channel, and across
the entrance to the Dardanelles from Brindisi, Italy, to the Albanian
coast. Also, battleships which should be unsinkable and provided with
longer-range guns than those of the enemy would be required. Perhaps
the combined navies of the world as arrayed against the Central Powers
could accomplish it, but unless their guns were more powerful and
far-reaching than the shore guns, even then they could not land an
invading army.
=Submarines vs. Submarines.=--Submarines to search for and sink other
submarines have been proposed in all sorts of forms and advocated in
the press under various titles, such as the "Bloodhounds of the Sea"
and other fantastic and sensational captions. Submarines cannot fight
submarines, because they cannot see each other, and if they are fitted
with noiseless machinery they cannot hear each other. Therefore one
might put thousands of submarines in the great ocean, and so long as
they kept submerged the chance of their ever finding or colliding with
one another would probably be not once in a year.
Derelicts have been known to keep afloat on the ocean for years,
although constantly searched for as a menace to navigation. Here the
searchers have had sight to aid them, and the object of their search
has floated on one plane, the surface of the water, while submarines
may navigate or remain at rest at various planes up to a depth of about
two hundred feet, which is equivalent to multiplying the area of the
ocean to be searched several times, and that in darkness, without the
aid of sight to assist. It is ridiculous to think that anything can be
accomplished except by the merest chance by one submarine searching for
another.
Our attention will now turn to consideration of devices of the second
class; namely, those which have been offered as a means of defence
against the submarine.
=Blinding Searchlight; Blinding Apparatus.=--_Blinding devices_ have
been proposed which aim to direct powerful searchlights against the
periscope so as to blind the commander. These are schemes based on
very false notions. Submarine commanders frequently have to con their
ship against the sun's rays, and have colored glasses to enable them
to withstand the intensity of the sun's rays, so that it would be
impossible to blind them this way. Further, I cannot imagine a more
desirable target for a commander to direct his torpedoes against
than a bright spot, either on the surface or submerged, as he knows
the searchlight is probably on what he wants to hit; it becomes an
illuminated bull's-eye for his target. Again, it has been proposed to
blind the periscope by putting a film of oil on the surface to obscure
the object glass of the periscope when it emerges through this oil,
and a member of one of the British commissions told me he knew of
shiploads of oil being pumped overboard, possibly for this purpose, or
to show the course of a periscope through its "slick." Some periscopes
have been built with means for squirting alcohol, gasoline, or other
substances to clear the object glass if ice or salt forms on it. A
device of this kind would clear off the oil.
=Nets; Plates.=--There have been many devices proposed for warding off
the torpedoes, the usual weapon of the submarine. The most common of
these schemes designate the use of nets or plates suspended from booms
carried out from the sides of the ship and extending down into the
water. Any device of this kind seriously handicaps the ship's speed,
and, if she is once sighted by a submarine, is almost sure to be come
up with and attacked. Plates, to be effective against a broadside
attack, would need to be the full length and extend to the full depth
of the ship. Now, skin friction of a ship's plating is the principal
resistance to be overcome in forcing a ship through the water up to
speeds of about ten knots, the average speed of the cargo-carrying
ship. If you increase the speed beyond ten knots, other resistances
come more prominently into effect, such as wave-making resistance, etc.
Now a ship afloat has two sides, while a plate suspended in the water
equal to the length and depth of the ship also must have two sides,
and thus presents nearly the same square feet of plate surface to the
friction of the passing waters as the two sides of the ship, and two
plates, one on each side, present nearly twice the area and thus very
materially reduce the speed. This resistance is further augmented by
the roll and pitch of the vessel, and in a severe storm the plates
would be unmanageable and of great danger to the ship itself. The
resistance of nets with its vertical members is much greater than that
of plates. To get some idea of what the resistance of a vertical rod
extending down into the water is, take a broom handle and attempt to
hold it vertical when it is extended down into the water from a launch
running at about ten knots; it is almost impossible to hold it. A net
with a mesh fine enough to catch a torpedo would consist of thousands
of vertical members as well as horizontal members extending down into
the water.
I have been informed by one naval architect of standing who
investigated this phase of the problem that nets of sufficient strength
to protect the sides of a ten-knot ship from a torpedo attack cut the
speed of the ship from ten knots down to two and one-half knots per
hour. It would therefore take a ship protected in this way four times
as long to make her voyage; her chance of discovery would therefore be
four times as great and her chance of destruction, if once discovered,
be almost certain, as a submarine could readily overtake her and
plant mines in her course or even tow a mine underneath her bottom and
explode it there, which would destroy the ship much more completely and
quickly than a Whitehead torpedo exploded against her side. Devices
have also been developed which enable a torpedo to dive under a net and
explode under a ship's bottom by a slightly delayed detonator.
Torpedoes have also been built with net-cutting devices, and they have
been known to penetrate a ship's plating and sink the vessel without
exploding. It is not an easy matter to stop a projectile weighing
nearly a ton speeding at thirty-five or forty miles an hour. I can see
no hope in stopping the submarine menace by any device in this class.
=Magnets.=--Some proposals have been made to divert the torpedo by
powerful magnets extended out beyond the sides of the ship or at the
ends--on the theory, I suppose, of fishing for little fish in a pan
of water--the Whitehead torpedo being built of steel in this country
and England. It is not generally known that the Schwartzkopf torpedo
built by the Germans is built of bronze, or at least it was when I went
through their works in Berlin several years ago. Even were it of steel,
I doubt if a magnet could be built powerful enough to attract or divert
a Whitehead steel torpedo from its course unless it passed very close
to the magnet, as any artificially erected magnetic force diminishes
in strength very rapidly as the distance from the object is increased.
Recall, for instance, the powerful magnets used in handling scrap and
pig iron; while they will lift pigs or billets of iron weighing tons
when in direct contact, they will not exert sufficient magnetic force
to lift any iron at a distance of only a few inches.
=Bombs.=--The throwing of bombs in the water to intercept the oncoming
torpedo might possibly divert its course if the torpedo were seen, but
of all the ships that have been lost how few have seen the torpedo
which did the damage! The white wake due to the air exhausted from the
engines of the torpedo is frequently seen, but the air wake does not
show on the surface from a torpedo running at any considerable depth
until after the torpedo itself has passed on, as it takes quite some
time for the air bubbles to reach the surface, and in a choppy sea the
wake is very difficult to see in any case.
=Discs.=--Whirling discs spinning through the water to catch the nose
of the torpedo and whirl it out of its course is one of the fanciful
schemes which has attracted some press notice. The horsepower required
to whirl the discs during one voyage would probably tax the full
capacity of the ship to provide fuel and power enough to keep them
whirling.
[Illustration: C-1, ONE OF THE LATER TYPE FRENCH SUBMARINES
French-Official
Courtesy of Sea Power & Pictorial Press]
=Unsinkable Ships.=--Unsinkable ships are possibly practical to a
limited extent. Numerous proposals of ship construction along this line
have been made, mostly of ships built up on the cellular system. Some
proposals have also been made for carrying the cargo in hermetically
sealed tanks that would assist in floating the ship if she were
torpedoed. The objections to the construction of vessels of this class
are its enormously increased cost over the ordinary cargo ship, the
reduced carrying capacity per ton of displacement of such vessels,
and the impossibility of preventing injury to ships of this sort to
such an extent as to make them unmanageable. Any surface ship, to meet
fully the submarine menace, must be not only _unsinkable, but it must
also be indestructible_. When a ship once becomes unmanageable and
incapable of getting away, a powerful mine or mines may be placed at
considerable depth under her bottom and the whole fabric blown up into
the air.
[Illustration: CARGO-CARRYING SUBMARINES OF THE AUTHOR'S DESIGN
They will carry 7500 tons of cargo on a surface displacement of 11,500
tons; their submerged displacement is about 13,500 tons.]
=Convoys.=--Convoying a merchant fleet offers perhaps some safety to
the individuals on the ships in case some of them are lost, but I
cannot see that it offers much protection to the fleet as a whole, as
the speed of the fleet is limited to that of the slowest ship, and the
smoke or appearance of the leading ships are more apt to give a waiting
slow-speed submarine time to catch up with the tail end of the fleet.
If it came to a gun fight the fleet might have the advantage, but in
experimental work I have frequently run in amidst a fleet of ships,
and their first knowledge of my presence was when the periscope was
extended above the surface. As it is only necessary to extend this for
a period of a few seconds' duration to get the range and bearing of
one of the ships to aim the torpedo, the chance of a gunner getting
the range and hitting the periscope is very slight, and, even if the
periscope were destroyed, it is easy to replace it with a spare one.
=Smoke Screens.=--To hide vessels in clouds of smoke so as to avoid
being seen by submarines has been proposed as a method for eluding the
U-boats. This procedure would really assist submarine commanders in
their search for prey, for the smoke would notify them of the presence
of vessels far below the horizon, whose location and course they would
otherwise not be aware of. They have a term in the British navy called
"firing into the Brown," which means firing at a group of vessels,
expecting that a certain percentage of hits will be made, depending on
how close a formation of ships is being kept; firing into the "smoke"
would be apt to get some. Smoke screens can be used effectively only
when the wind happens to be proportionate to the speed of the ships and
blowing in the right direction. With a head wind or a strong side wind
some of the vessels forming the convoy are sure to be exposed to attack.
=Zigzag.=--Steering zigzag courses adds to the time of crossing from
one port to another, and affords only a slight measure of additional
safety, as a ship running a zigzag course takes much longer to make
a crossing, and is therefore longer exposed to danger; besides, this
process adds very materially to the cost of the voyage. It probably
does add somewhat to her chances of escape, as a submarine lying in
wait anticipating that she will pass within torpedo range might be
fooled by her zigzagging out of the way. On the other hand, a submarine
might be lying in wait too far to one side of her course to be able to
intercept her, and the ship might just as likely as not, not knowing
she was there, zigzag right toward her and get caught.
In facing the submarine problem, the nations at war with Germany are
thus forced to adopt tactics of three kinds: First, to destroy the
enemy submarines--I have been informed from reliable sources that
England has over five thousand vessels searching for U-boats; second,
to make cargo vessels invulnerable to torpedo attacks; and, thirdly,
to elude and escape the U-boats. No great measure of success, no great
results, have come out of attempts of the first two orders; the U-boats
have in general gone unscathed, and they have inflicted damage of such
an appalling nature as to terrify those cognizant of the shipping needs
of Europe. In my judgment, however, efforts to combat the submarine
should be concentrated on devising ways and means to elude it; this is
the only solution which promises results. I shall therefore devote the
remainder of this chapter to a discussion of the problem of eluding
submarines and how it may best be accomplished.
=Cargo Submarines.=--In my judgment, the only way that any nation will
be able ultimately to continue its commerce with any degree of safety
or certainty when blockaded by submarines will be by the construction
of large merchant submarines which will be able to evade the enemy
U-boats successfully.
I have pointed out above that "submarines cannot fight submarines,"
because they cannot see or locate each other. It is this very thing
which will enable the cargo-carrying submarine to evade the military
submarine. They are also able to evade all surface craft, either friend
or foe. Captain Paul Koenig, of the _Deutschland_, told me that most
of his journey in the _Deutschland_ was upon the surface. He stated
that her low visibility enabled him to see all approaching ships before
they could see her, and that it was only necessary for him to submerge
and rest until the surface ship had passed on her way. The tactics of
the larger cargo-carrying submarines would be the same. They need not
have much radius of action when submerged; all they need to do is to
hide until the danger has passed. If desired, however, their radius of
submerged action may be increased to equal or largely exceed that of a
military submarine, but this would unnecessarily increase their cost
of construction; otherwise the cost of building such vessels should
not exceed twenty-five per cent. more than the cost of constructing a
first-class surface ship.
Now I have prepared a few diagrams showing the advantage of various
types of vessels in evading the submarine, and of these I shall treat
immediately, as they illustrate the points of my contention perfectly.
There was a time when everybody thought the earth was flat, but now
I believe it is generally conceded that it is round. Every one knows
that when the sun or moon sinks beneath the horizon it cannot be seen,
neither can anything else which is below the horizon, so if the horizon
intervenes between two distant observers they cannot see each other.
Now by referring to our text-books we find that if an observer is
stationed at a height of fifteen feet above the surface of the sea the
horizon is five and one-eighths miles distant, so that if there were
another observer stationed on the other side of the horizon at the same
distance and height from the surface of the sea they could not see each
other, as the surface of the earth or sea, being round, would stand up
like a hill between them.
[Illustration: THE "DEUTSCHLAND"
By Courtesy of Motorship
The "Deutschland" was the first submarine cargo-carrier to cross the
Atlantic Ocean. She was under the command of Captain Paul Koenig and
proved the practicability of running the English blockade four times
before war between Germany and the United States caused her owners to
discontinue her sailings. Had war not come between the two countries,
her German owners would undoubtedly have had submarine cargo-carrying
vessels making weekly sailings between the United States and Germany.]
The diagram shown herewith shows the distance of horizon in miles from
0 to two hundred feet elevation above the surface of the water.
I have drawn a sketch--in which the scale of distance is exaggerated
in order to better illustrate my meaning--of the earth's surface to
show the comparative visibility of vessels when seen from a military
submarine, lying in wait, with periscope extended fifteen feet above
water. Now take such ships as the _Lusitania_, shown in position No.
5 on the diagram, with her smoke-stacks extending over one hundred
feet above the surface of the sea; their tops would appear above the
horizon and become visible to a distant observer with a powerful glass,
stationed at, say, fifteen feet above the surface, at a distance of
about eighteen and three-eighths miles. Her smoke-stack would also
become visible through a telescopic periscope, the object glass of
which was extended fifteen feet above the surface, while men seated in
a rowboat could not see each other because of the intervening "hill,"
so to speak, at a distance of four miles apart. If they were under
water in a submarine they could not see each other at all unless they
had the periscopes elevated above the surface. In that case it would
not be possible for one periscope to see another at any considerable
distance, because the periscope is such a small object, and vision
through it does not compare with natural vision, owing to the fact that
there is considerable loss of light in passing the image of external
objects through lenses and prisms. Hence it has been found necessary
to reduce the field of vision to about one-half that of natural vision
to give the effect of true distance, and as soon as twilight falls it
is practically useless. I have taken fifteen feet above the surface
without the submarine's conning tower showing, for if her conning tower
is shown above the surface she is in danger of being herself discovered.
From the above data we are able to determine the probability of being
discovered. We take the case of the largest and fastest ocean liners,
such as the _Lusitania_ as one illustration. We will assume that the
_Lusitania_ is making her maximum speed of about twenty-five knots,
which is about the maximum of speed yet attained in a large surface
freight-and passenger-carrying ship, and from our scale of vision as
applied to upper diagram No. 5 we see that her top works will become
visible above the horizon at a distance of eighteen and three-eighths
miles from the periscope of the submarine. The commander in the
submarine, by using his range and direction finder with which all
military submarines are fitted, finds the ship to be pursuing a course
and speed that will cause her to pass probably within ten miles of the
submarine station in about thirty-five minutes, which is too far off to
attack by torpedo. Now, while submarines have a submerged speed of only
about ten knots, the commander is quickly able to ascertain that he can
intercept the twenty-five-knot boat by laying his own course at right
angles to the approaching ship, and that, if the ship keeps her course
and speed, in thirty-five minutes he can be within torpedo range, as
will be seen by reference to this sketch (see diagram, position No. 5).
[Illustration: DIAGRAM TO ILLUSTRATE THE COMPARATIVE VISIBILITY AND
CONSEQUENTLY THE COMPARATIVE SAFETY OF SURFACE SHIPS AND CARGO-CARRYING
SUBMARINES]
Now take for another comparison a slow-speed merchantman of the
tramp type making ten knots, which is about the economical speed for
this class of ship. Her smoke might be the first thing to betray
her approach, but for purposes of comparison take her smoke-stack
also, which is the first solid portion of the ship to appear. The
smoke-stacks of this class of vessel would probably not be over forty
feet in height above water level, therefore, if she were making the
same course as the high-speed ship, it will be observed by referring to
diagram, position No. 4, and the distance and speeds mentioned thereon,
that the submarine at a speed of ten knots has more time to get nearer
the course of the approaching ship and can have more time to calculate
the enemy's speed of approach and direct course, and thus launch his
torpedo with more certainty of making a hit. But assume that this
approaching slow-speed ship had no solid opaque portion extending over
fifteen feet above the surface of the water, as is the case in a cargo
submarine as shown in position No. 3 on the diagram of the earth's
surface. One now sees that she would pass the waiting submarine
below the horizon, and the intervening round of the sea's surface would
prevent the submarine from seeing her; thus she would pass by unseen
and in safety.
The above series of diagrams will show the percentage of safety of
ships of different characteristics when coming within the range of
visibility of a submarine lying on the ocean highway waiting for
passing ships; the submarine is assumed to have a submerged speed of
ten knots in each instance. From an analysis of these diagrams it
cannot be denied that practically one hundred per cent. safety could
be secured could these cargo-carrying submarines cross the ocean from
one friendly port to another and remain invisible during the entire
journey, but at the present time this is impossible, because there
is no known means of supplying sufficient power for long under-water
voyages without drawing on the upper air in large quantities to assist
combustion in either prime or secondary power-generating machinery.
The diagram plainly shows that a cargo-carrying submarine running
awash, with her periscope and air intakes only above the water line,
may approach within about five and three-quarters miles of any waiting
military submarine without danger of being seen, as her "wake" would
be below the horizon. Such cargo-carrying submarines can be built and
can cross the Atlantic Ocean in this condition at a speed of about ten
knots, and by maintaining a sharp lookout would have as much chance of
seeing a military submarine as the military submarine would have of
seeing them; and by the application of certain tried devices which I do
not feel it proper to disclose at this time, but which are within the
knowledge of our government authorities, the range of visibility can,
I believe, be reduced to less than one mile. This type of vessel can
almost instantly become entirely invisible by submerging at the least
intimation of danger.
Such a type of vessel travelling with a freeboard of five feet would
become visible to a submarine lying in ambush when she approached
within eight miles. This increases the area of danger from one hundred
and three square miles, as shown in diagram, position No. 1, in the
first instance to two hundred and one square miles, as per diagram
corresponding to position No. 2, but in comparison with the usual type
of surface cargo-carrying ship of the so-called tramp type she is
comparatively safe, as she has the ability to submerge in less than two
minutes; and it is hardly likely that she would be attacked without
warning, for fear she might be a friendly military submarine. Any
communication in the way of wireless, sound, or other signals would,
if she were a merchant ship, give her warning, and she would at once
submerge, as her only business would be to deliver her cargo and not
communicate with or expose herself to _either friend or foe_. When far
from land she might take a chance and navigate entirely on the surface
with a freeboard of fifteen feet, in which condition she can make a
speed of eleven knots, as her position No. 3, on the surface of the
ocean. This increases the danger area to about three hundred and thirty
square miles, as on diagram, position No. 3, about three times the
danger area shown on position No. 1, but as the area to be covered by
the military submarine on the high seas, far from land, is also much
greater, the real danger would be proportionately less than that with
the lower visibility in a more thickly infested zone.
[Illustration: TORPEDO BEING FIRED FROM THE DECK TUBES OF THE SUBMARINE
"SEAL"
This vessel was fitted with two double-barrel torpedo guns, housed in
a superimposed superstructure. These four torpedoes could be fired to
either broadside. The above photograph shows a torpedo in the act of
leaving one of these tubes above water. They may be discharged either
above or below the surface.]
=High Speed.=--Speed is better than no defence, but no one would
consider building twenty-five-knot freighters. The cost would be far
out of proportion to the service. So long as U-boats do not betray
their presence, a fast vessel is almost as liable as a slower one
of less freeboard or lower top hamper. One can never tell where the
submarine may be lurking, and her capacity to harm is determined by her
ability to locate her prey. There are three means available to her to
locate her target: first, her own sight; second, her sound-detecting
devices; third, by wireless directions given to her by others who may
advise her of the vessel's position. Her own sight is the best and
usual means for locating her target. The above diagrams show that the
largest and fastest ships can be located at much greater distances than
the low visibility ships, and that the area of visibility becomes the
area of danger, which is practically ten times greater in an expensive,
large, high-speed liner over that of the comparatively low-cost
cargo-carrying submarine.
[Illustration: BRITISH SUBMARINE NO. 3 PASSING NELSON'S OLD FLAGSHIP
"VICTORY"
This submarine is of the Holland type, similar to the U. S. "Adder" and
"Moccasin." This illustration shows the radical change made in naval
warfare in one hundred years.]
One should not imagine that the Germans are carrying on this campaign
at random. It is well organized and systematic. Each vessel that
comes in sight of a submarine is a marked vessel, and even if she is
the fastest vessel afloat, she may speed unwittingly into a trap set
for her by wireless. So long as she cannot disappear she has no real
ability to elude. On the other hand, the cargo-carrying submarine of
low speed has both these advantages: she has low visibility and the
capability of disappearance. She may become invulnerable when danger
threatens. She has all of the qualities possessed by her enemies. She
may beat them at their own game. Vessels of the ordinary type will
suffice in no way to meet the great problem presented by the U-boats.
The cargo submarine, however, readily meets all the needs of the
situation. This is the sole method of which I am cognizant by means
of which a submarine blockade and the destruction of cargo-carrying
vessels can be overcome with safety and with certainty. I have expected
the Germans would blockade our own ports, as it is easily possible for
them to do so; I believe the reason they have not done so thus far
is because of political reasons, as it would undoubtedly be to their
advantage to have our trade after the war, which they might not have if
they arouse our hatred any more than they already have.