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 aloft, 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 humanity, 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.
Furthermore it is stated to be fitted with a small gyroscope in the
manner of the torpedo used in the seas, for the purpose of maintaining
direction during flight, but upon this point there is considerable
divergence of opinion among technicians, the general idea being that
the torpedo depends upon an application of the principle of the ordinary
rocket rather than upon a small engine such as is fitted to the ordinary
torpedo. The employment of a slow combustible ensures the maintenance
of the missile in the air for a period exceeding that of the ordinary
shell. It is claimed by the Germans that this projectile will keep aloft
for half-an-hour or more, but this is a phantasy. Its maintenance of
flight is merely a matter of minutes.
The belated appearance of this much-lauded projectile and its restricted
use suggest that it is unreliable, and perhaps no more effective than
the aerial torpedo which appeared in the United States during the
Spanish-American War, and proved a complete failure. An effective and
reliable means of combating or frustrating a dirigible attack, other
than by gun-fire or resort to the drastic remedy of ramming the enemy,
has yet to be devised.