Aeroplanes and Dirigibles of War

F >> Frederick A. Talbot >> Aeroplanes and Dirigibles of War

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Attempts have been and still are being made to adapt an explosive
projectile to this gun, but so far the measure of success
achieved has not proved very promising. There are immense
difficulties connected with the design of an explosive shell of
this class, charged with a high explosive, especially in
connection with the timing. So far as dependence upon percussive
detonation is concerned there is practically no difficulty.
Should such a missile strike, say, the motor of an aeroplane, or
even the hull of the craft itself, the latter would be
practically destroyed. But all things considered, it is
concluded that more successful results are likely to be achieved
by the armour-piercing bullet striking the mechanism than by an
explosive projectile.

The Krupp company fully reahsed the difficulties pertaining to
the projectile problem in attacks upon aerial craft. So far as
dirigibles are concerned shrapnel is practically useless,
inasmuch as even should the bag be riddled by the flying
fragments, little effective damage would be wrought--the craft
would be able to regain its haven. Accordingly efforts were
concentrated upon the perfection of two new types of projectiles,
both of which were directed more particularly against the
dirigible. The one is the incendiary shell--obus fumigene--while
the other is a shell, the contents of which, upon coming into
contact with the gas contained within the gas-bag, set up certain
chemical reactions which precipitate an explosion and fire.

The incendiary shells are charged with a certain compound which
is ignited by means of a fuse during its flight. This fuse
arrangement coincides very closely with that attached to ordinary
shrapnel, inasmuch as the timing may be set to induce ignition
at different periods, such as either at the moment it leaves the
gun, before, or when it strikes the envelope of the dirigible.
The shell is fitted with a "tracer," that is to say, upon
becoming ignited it leaves a trail of smoke, corresponding with
the trail of a rocket, so that its passage through the air may be
followed with facility. This shell, however, was designed to
fulfil a dual. Not only will it fire the gaseous contents out of
the dirigible, but it has an explosive effect upon striking an
incombustible portion of the aircraft, such as the machinery,
propellers or car, when it will cause sufficient damage to throw
the craft out of action.

The elaborate trials which were carried out with the obus
fumigene certainly were spectacular so as they went. Two small
spherical balloons, 10 feet in diameter, and attached to 1,000
feet of cable, were sent aloft. The anti-aircraft guns
themselves were placed about 5,1OO feet distant. Owing to the
inclement weather the balloons were unable to attain a height of
more than 200 feet in a direct vertical line above the ground.
The guns were trained and fired, but the one balloon was not hit
until the second round, while the third escaped injury until the
fifth round. When struck they collapsed instantly. Though the
test was not particularly conclusive, and afforded no reliable
data, one point was ascertained--the trail of smoke emitted by
the shell enabled its trajectory to be followed with ease. Upon
the conclusion of these trials, which were the most successful
recorded, quick-firing tests in the horizontal plane were carried
out. The best performance in this instance was the discharge of
five rounds in eight seconds. In this instance the paths of the
projectiles were simple and easy to follow, the flight of the
shell being observed until it fell some 18,670 feet away. But
the Krupp firmhave found that trials upon the testing ground with
a captive balloon differ very materially from sterntests in the
field of actual warfare. Practically nothing has been heard of
the two projectiles during this war, as they have proved an
absolute failure.

Some months ago the world was startled by the announcement that
the leading German armament firm had acquired the whole of the
interest in an aerial torpedo which had been evolved by the
Swedish artillerist, Gustave Unge, and it was predicted that in
the next war widespread havoc would be wrought therewith.
Remarkable claims were advanced for this projectile, the foremost
being that it would travel for a considerable distance through
the air and alight upon the objective with infallible accuracy.
The torpedo in question was subjected to exacting tests in Great
Britain, which failed to substantiate all the claims which were
advanced, and it is significant to observe that little has been
heard of it during the present conflict. It is urged in certain
technical quarters, however, that the aerial torpedo will prove
to be the most successful projectile that can be used against
aircraft. I shall deal with this question in a later chapter.

During the early days of the war anti-aircraft artillery appeared
to be a much overrated arm. The successes placed to its credit
were insignificant. This was due to the artillerymen being
unfamiliar with the new arm, and the conditions which prevail
when firing into space. Since actual practice became possible
great advances in marksmanship have been recorded, and the
accuracy of such fire to-day is striking. Fortunately the airman
possesses the advantage. He can manoeuvre beyond the range of
the hostile weapons. At the moment 10,000 feet represents the
extreme altitude to which projectiles can be hurled from the arms
of this character which are now in use, and they lack
destructiveness at that range, for their velocity is virtually
expended.

Picking up the range is still as difficult as ever. The practice
followed by the Germans serves to indicate the Teuton
thoroughness of method in attacking such problems even if success
does not ensue. The favourite German principle of disposing
anti-aircraft artillery is to divide the territory to be
protected into equilateral triangles, the sides of which have a
length of about six miles or less, according to the maximum
effective range of the pieces at an elevation of 23 1/2 degrees.

The guns are disposed at the corners of the triangles as
indicated in Figs. 13-14. Taking the one triangle as an example,
the method of picking up the range may be explained as follows.
The several guns at the comers of the triangle, each of which can
be trained through the 360 degrees in the horizontal plane, are
in telephonic touch with an observer O stationed some distance
away. The airman A enters the area of the triangle. The
observer takes the range and communicates with the gunner B, who
fires his weapon. The shell bursts at 1 emitting a red flame and
smoke. The observer notes the altitude and relative position of
the explosion in regard to the aircraft, while gunner B himself
observes whether the shell has burst to the right or to the left
of the objective and corrects accordingly. The observer commands
C to fire, and another shell is launched which emits a yellow
flame and smoke. It bursts at 2 according to the observer, while
gunner C also notes whether it is to the right or to the left of
the target and corrects accordingly. Now gunner D receives the
command to fire and the shell which explodes at 3 throws off a
white flame and smoke. Gunner D likewise observes whether there
is any deviation to right or left of the target and corrects in a
similar manner. From the sum of the three rounds the observer
corrects the altitude, completes his calculations, and
communicates his instructions for correction to the three
gunners, who now merely train their weapons for altitude. The
objective is to induce the shells hurled from the three corners
of the triangle to burst at a common point 4, which is considered
to be the most critical spot for the aviator. The fire is then
practically concentrated from the three weapons upon the apex of
a triangular cone which is held to bring the machine within the
danger zone.

This method of finding the range is carried out quickly--two or
three seconds being occupied in the task. In the early days of
the war the German anti-aircraft artillerymen proved sadly
deficient in this work, but practice improved their fire to a
marvellous degree, with the result that at the moment it is
dangerous for an aviator to essay his task within an altitude of
6,000 feet, which is the range of the average anti-aircraft gun.

The country occupied by a belligerent is divided up in this
manner into a series of triangles. For instance, a machine
entering hostile territory from the east, enters the triangle
A-B-C, and consequently comes within the range of the guns posted
at the comers of the triangle. Directly he crosses the line B-C
and enters the adjacent triangle he passes beyond the range of
gun A but comes within the range of the gun posted at D, and
while within the triangular area is under fire from the guns
B-C-D. He turns and crosses the line A-C, but in so doing enters
another triangle A-C-E, and comes range of the gun posted at E.

The accompanying diagram represents an area of country divided up
into such triangle and the position of the guns, while the circle
round the latter indicate the training arc of the weapons, each
of which is a complete circle, in the horizontal plane. The
dotted line represents the aviator's line of flight, and it will
be seen that no matter how he twists and turns he is always
within the danger zone while flying over hostile territory. The
moment he outdistances one gun he comes within range of another.

The safety of the aviator under these circumstances depends upon
his maintaining an altitude exceeding the range of the guns
below, the most powerful of which have a range of 8,000 to 10,000
feet, or on speed combined with rapid twisting and turning, or
erratic undulating flight, rendering it extremely difficult for
the gun-layer to follow his path with sufficient celerity to
ensure accurate firing.

At altitudes ranging between 4,000 and 6,000 feet the aeroplane
comes within the range of rifle and machine-gun firing. The
former, however, unless discharged in volleys with the shots
covering a wide area, is not particularly dangerous, inasmuch as
the odds are overwhelmingly against the rifleman. He is not
accustomed to following and firing upon a rapidly moving
objective, the result being that ninety-nine times out of a
hundred he fails to register a hit. On the other hand the
advantage accruing from machine-gun fire is, that owing to the
continuous stream of bullets projected, there is a greater
possibility of the gun being trained upon the objective and
putting it hors de combat.

But, taking all things into consideration, and notwithstanding
the achievements of the artillerist, the advantages are
overwhelmingly on the side of the aviator. When one reflects
upon the total sum of aircraft which have been brought to earth
during the present campaign, it will be realised that the number
of prizes is insignificant in comparison with the quantity of
ammunition expended.

CHAPTER XVI
MINING THE AIR

While the anti-aircraft gun represents the only force which has
been brought to the practical stage for repelling aerial attack,
and incidentally is the sole offensive weapon which has
established its effectiveness, many other schemes have been
devised and suggested to consummate these ends. While some of
these schemes are wildly fantastic, others are feasible within
certain limitations, as for instance when directed against
dirigibles.

It has been argued that the atmosphere is akin to the salt seas;
that an aerial vessel in its particular element is confronted
with dangers identical with those prevailing among the waters of
the earth. But such an analogy is fallacious: there is no more
similarity between the air and the ocean than there is between an
airship and a man-of-war. The waters of the earth conceal from
sight innumerable obstructions, such as rocks, shoals, sandbanks,
and other dangers which cannot by any means be readily detected.

But no such impediments are encountered in the ether. The craft
of the air is virtually a free age in the three dimensions. It
can go whither it will without let or hindrance so long as the
mechanical agencies of man are able to cope with the influences
of Nature. It can ascend to a height which is out of all
proportion to the depth to which the submarine can descend in
safety. It is a matter of current knowledge that a submarine
cannot sink to a depth of more than 250 feet: an aerial vessel is
able to ascend to 5,000, 8,000, or even 10,000 feet above the
earth, and the higher the altitude it attains the greater is its
degree of safety. The limit of ascension is governed merely by
the physical capacities of those who are responsible for the
aerial vessel's movement.

It is for this reason that the defensive measures which are
practised in the waters of the earth are inapplicable to the
atmosphere. Movement by, or in, water is governed by the depth
of channels, and these may be rendered impassable or dangerous to
negotiate by the planting of mines. A passing ship or submarine
may circumvent these explosive obstructions, but such a
successful manoeuvre is generally a matter of good luck. So far
as submarines are concerned the fact must not be over looked that
movements in the sea are carried out under blind conditions: the
navigator is unable to see where he is going; the optic faculty
is rendered nugatory. Contrast the disability of the submarine
with the privileges of its consort in the air. The latter is
able to profit from vision. The aerial navigator is able to see
every inch of his way, at least during daylight. When darkness
falls he is condemned to the same helplessness as his confrere in
the waters below.

A well-known British authority upon aviation suggested that
advantage should be taken of this disability, and that the air
should be mined during periods of darkness and fog to secure
protection against aerial invasion. At first sight the proposal
appears to be absolutely grotesque, but a little reflection will
suffice to demonstrate its possibilities when the area to be
defended is comparatively limited. The suggestion merely
proposes to profit from one defect of the dirigible. The latter,
when bent upon a daring expedition, naturally prefers to make a
bee-line towards its objective: fuel considerations as a matter
of fact compel it to do so. Consequently it is possible, within
certain limits, to anticipate the route which an invading craft
will follow: the course is practically as obvious as if the
vessel were condemned to a narrow lane marked out by sign-posts.
Moreover, if approaching under cover of night or during thick
weather, it will metaphorically "hug the ground." To attempt to
complete its task at a great height is to court failure, as the
range of vision is necessarily so limited.

Under these circumstances the mining of the air could be carried
out upon the obvious approaches to a threatened area. The mines,
comprising large charges of high-explosive and combustible
material, would be attached to small captive balloons similar to
the "sounding balloons" which are so much used by meteorologists
in operations for sounding the upper strata of the atmosphere.
These pilot balloons would be captive, their thin wires being
wound upon winches planted at close intervals along the
coast-line. The balloon-mines themselves would be sent to
varying heights, ranging from 1,000 to 5,000 feet, and with
several attached to each cable, the disposition of the mines
in the air in such an irregular manner being in fact closely
similar to the practice adopted in the mining of a channel for
protection against submarines and hostile ships.

The suggestion is that these mines should be sent aloft at dusk
or upon the approach of thick and foggy weather, and should be
wound in at dawn or when the atmosphere cleared, inasmuch as in
fine weather the floating aerial menace would be readily detected
by the pilot of a dirigible, and would be carefully avoided. If
the network were sufficiently intricate it would not be easy for
an airship travelling at night or in foggy weather to steer clear
of danger, for the wires holding the balloons captive would be
difficult to distinguish.

The mines would depend upon detonators to complete their work,
and here again they would bear a close resemblance to sea-mines.
By looping the mines their deadliness could be increased. The
unsuspicious airship, advancing under cover of darkness or thick
weather, might foul one of the wires, and, driving forward, would
tend to pull one or more mines against itself. Under the force
of the impact, no matter how gentle, or slight, one or more of
the detonating levers would be moved, causing the mine to
explode, thus bursting the lifting bag of the vessel, and firing
its gaseous contents. An alternative method, especially when a
cable carried only a single mine, would be to wind in the captive
balloon directly the wire was fouled by an invading aerial craft,
the process being continued until the mine was brought against
the vessel and thereby detonated.

Another proposed mining method differs materially in its
application. In this instance it is suggested that the mines
should be sent aloft, but should not be of the contact type, and
should not be fired by impact detonators, but that dependence
should be placed rather upon the disturbing forces of a severe
concussion in the air. The mines would be floating aoft, and
the advance of the airship would be detected. The elevation
of the mines in the vicinity of the invading craft would be
known, while the altitude of the airship in relation thereto
could be calculated. Then, it is proposed that a mine within d
certain radius of the approaching craft, and, of course, below
it, should be fired electrically from the ground. It is
maintained that if the charge were sufficiently heavy and an
adequate sheet of flame were produced as a result of the
ignition, an airship within a hundred yards thereof would be
imperilled seriously, while the other mines would also be fired,
communicating ignition from one to the other. The equilibrium
of the airship is so delicate that it can be readily upset, and
taking into account the facts that gas is always exuding from
the bag, and that hydrogen has a tendency to spread somewhat in
the manner of oil upon water, it is argued that the gas would be
ignited, and would bring about the explosion of the airship.

Another method has even been advocated. It is averred in
authoritative circles that when the aerial invasion in force of
Great Britain is attempted, the Zeppelins will advance under the
cover of clouds. Also that the craft will make for one
objective--London. Doubtless advantage will be taken of clouds,
inasmuch as they will extend a measure of protection to the craft,
and will probably enable the invading fleet to elude the vigilance
of the aeroplane scouts and patrols. Under these circumstances it
is suggested that balloon-mines should be sent aloft and be
concealed in the clouds. It would be impossible to detect the
wires holding them captive, so that the precise location of the
lurking danger would not be divined by the invader. Of course,
the chances are that the invading airship would unconsciously
miss the mines; on the other hand the possibilities are equally
great that it would blunder into one of these traps and be blown
to atoms.

An English airman has recently suggested a means of mining
invading Zeppelins which differs completely from the foregoing
proposals. His idea is that aeroplanes should be equipped with
small mines of the contact type, charged with high explosives,
and that the latter should be lowered from the aeroplane and be
trawled through the atmosphere. As an illustration I will suppose
that a hostile aircraft is sighted by a patrolling aeroplane.
The pilot's companion in the latter immediately prepares his
aerial mine, fixing the detonator, and attaching the mine to the
wire. The latter is then dropped overboard, the wire being paid
out from a winch until it has descended to the level of the
hostile craft. The airman now manoeuvres in the air circling
about the airship, dragging his mine behind him, and endeavouring
to throw it across or to bring it into contact with the airship
below. Naturally the latter, directly it observed the airman's
object, would endeavour to elude the pursuing trawling mine,
either by crowding on speed or by rising to a greater altitude.
The aeroplane, however, would have the advantage both in point of
speed and powers of climbing, while there is no doubt that the
sight of the mine swinging in the air would exert a decisive
moral effect upon those in the airship.

Attempts to render the mine harmless by discharging it
prematurely with the aid of rifle and machine-gun fire would, of
course, be made by the crew of the airship, but the trawling mine
would prove a very difficult target to strike. If such a missile
were used against an airship of the proportions of a Zeppelin the
mine would inevitably be trawled across the vessel sooner or
later. Once the airship had been fouled, the aviator would
merely have to drive ahead, dragging the wire and its charge
across the gas-bag until at last one of the contact levers of the
mine was moved by being dragged against some part of the vessel,
when the mine would be exploded. In such operations the aviator
would run a certain risk, as he would be more or less above the
airship, and to a certain degree within the zone of the ultimate
explosion. But there is no doubt that he would succeed in his
"fishing" exploit within a very short time.

This ingenious scheme has already been tested upon a small scale
and has been found effective, the trawling bomb being drawn
across its target and fired by contact within a few minutes. The
experiment seems to prove that it would be simpler and more
effectual to attack a hostile aircraft such as a Zeppelin in this
manner than to drop free bombs at random. Moreover, we cannot
doubt that the sight of a mine containing even ten or twelve
pounds of high explosive dangling at the end of a wire would
precipitate a retreat on the part of an airship more speedily
than any other combative expedient.

The advocate of this mine-trawling method, who is a well-known
aviator, anticipates no difficulty in manoeuvring a mine weighing
30 pounds at the end of 300 feet of fine wire. Success depends
in a great measure on the skill of the aviator in maintaining a
constant tension upon the line until it falls across its
objective.

The process calls for a certain manifestation of skill in
manoeuvring the aeroplane in relation to the airship, judgment of
distance, and ability to operate the aeroplane speedily. The
rapid ascensional capability of the airship, as compared with
that of the aeroplane, is a disadvantage, but on the other hand,
the superior mobility and speed of the aeroplane would tell
decisively for success.

Among the many wonders which the Krupp organisation is stated to
have perfected, and which it is claimed will create considerable
surprise, is the aerial torpedo. Many of the Krupp claims are
wildly chimerical, as events have already proved, but there is no
doubt that considerable effort has been expended upon this latest
missile, for which the firm is said to have paid the inventor
upwards of L25,000--$125,000. Curiously enough the projectile
was perfected within gunshot of the British aerodrome of Hendon
and is stated to have been offered to the British Government at
the time, and to have met with a chilling reception. One fact,
however, is well established. The inventor went to Germany, and
submitted his idea to Krupp, by whom it was tested without delay.
Upon the completion of the purchase, the great armament
manufacturers did not fail to publish broadcast the fact that
they had acquired a mysterious new terror of the skies. That was
some three years ago, and in the interval the cleverest brains of
the German firm have been steadily devoting their time and
energies to the improvement of the missile, the first appearance
of which was recorded, in a somewhat hazy manner, in the closing
days of December.

While the exact mechanism of this missile is a secret, the
governing principles of its design and operation are known to a
select few technicians in this country. Strange to say, the
projectile was designed in the first instance in the interests of
peace and humanty, but while engaged upon his experiments the
inventor suddenly concluded that it would be a more profitable
asset if devoted to the grim game of war. At the time the
military significance of the airship and the aeroplane were
becoming apparent; hence the sudden diversion of the idea into a
destructive channel.

This aerial torpedo is a small missile carrying a charge of high
explosive, such as trinitrotoluene, and depends for its
detonation upon impact or a time fuse. It is launched into the
air from a cradle in the manner of the ordinary torpedo, but the
initial velocity is low. The torpedo is fitted with its own
motive power, which comes automatically into action as the
missile climbs into the air. This self-contained energy is so
devised that the maximum power is attained before the missile has
lost the velocity imparted in the first instance, the result
being that it is able to continue its flight in a horizontal
direction from the moment it attains the highest point in its
trajectory, which is naturally varied according to requirements.
But there is no secret about the means of propulsion. The body
is charged with a slow-burning combustible, in the manner of the
ordinary rocket, whereby it is given a rapid rotary motion.

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