Although the Zeppelin undoubtedly has been over-rated by the forces to
which it is attached, at the same time it must not be under-estimated by
its detractors. Larger and more powerful vessels of this type have been,
and still are being, constructed, culminating, so far as is known, in
the "L-5," which is stated to have a capacity of about 1,000,000 cubic
feet, and to possess an average speed of 65 miles per hour.
While it is generally maintained that the Zeppelins will prove
formidable in attack, greater reliance is being placed upon the
demoralising or terrifying effect which they are able to exercise. Owing
to the fact that from 3 to 5 tons of fuel--say 900 to 1,500 gallons of
gasoline or petrol--can be carried aboard, giving them a wide radius of
action, it is doubtful whether they could travel from Cologne to London
and back upon a single fuel charge, since such a raid would entail a
journey of about 600 miles. The latest types of this craft are said to
possess a high ascensional speed, which offers a distinct protection
against aeroplane attack. According to such official information as
has been vouchsafed, a Zeppelin, when hard pressed, is able to rise
vertically 3,500 feet in about three minutes. This is far in excess of
the ascensional speed of even the speediest aeroplane, of course, the
penalty for such a factor has to be paid: the loss of gas is appreciable
and may lead to the craft's ultimate undoing. At the same time, however,
it is able to maintain the superior position as compared with the
aeroplane for a considerable period: the upper reaches of the air are
its sanctuary.
Nor must the nocturnal activities of the Zeppelin be overlooked. So far
as night operations by these vessels are concerned, little has leaked
out, so that the possibilities of the airship in this direction are
still somewhat hypothetical. The fact remains, however, that it is
night movements which perhaps are the most to be dreaded by the enemy.
According to official German sources of information the latest types of
Zeppelins are engined by "noiseless" motors. There is nothing remarkable
in this feature, since the modern motor-car virtually answers to this
description, although in this instance quietness is obtained for the
most part by recourse to the sleeve-valve engine. Still, the ordinary
Otto-cycle internal combustion engine can be rendered almost silent by
the utilisation of adequate muffling devices, which, in the Zeppelin,
are more possible of incorporation than in the aeroplane, because the
extra weight imposed by this acquisition is a minor consideration in
comparison with the lifting power of the vessel.
Night operations, however, have not proved eminently successful. The
very darkness which protects the aerial prowler also serves a similar
purpose in connection with its prey. But aerial operations under the
cover of darkness are guided not so much by the glare of lights from
below as betrayal by sound. The difference between villages and cities
may be distinguished from aloft, say at 1,500 to 3,000 feet, by the hum
which life and movement emit, and this is the best guide to the aerial
scout or battleship. The German authorities have made a special study
of this peculiar problem, and have conducted innumerable tests upon the
darkest nights, when even the sheen of the moon has been unavailable,
for the express purpose of training the aerial navigators to discover
their position from the different sounds reaching them from below. In
other words, the corsair in the skies depends more upon compass and
sound than upon compass and vision when operating after dark. The
searchlights with which the Zeppelins are equipped are provided merely
for illuminating a supposed position. They are not brought into service
until the navigator concludes that he has arrived above the desired
point: the ray of light which is then projected is merely to assist the
crew in the discharge of the missiles of destruction.
The Zeppelin, however, owing to its speed, both in the horizontal and
vertical planes, is essentially a unit for daylight operations. The
other airships which Germany possesses, and which for the most part are
of the non-rigid type, are condemned to daylight operations from
the character of their design. Owing to their low speeds they may be
dismissed as impossible aerial vessels for hazardous work and are not
regarded by the German authorities as all-round airships of war.
Craft of the air are judged in Germany from the one standard only. This
may be a Teutonic failing, but it is quite in keeping with the Teutonic
spirit of militarism. Commercialism is a secondary factor. To the German
Emperor an airship is much what a new manufacturing process or machine
is to the American. Whereas the latter asks, "How much will it save
me on the dollar?" to the War Lord of Germany--and an airship
notwithstanding its other recommendatory features is judged solely from
this standpoint--the question is "What are its military qualifications?"
When the semi-rigid airship "V-I" was brought before the notice of the
German military department the pressing point concerning its military
recommendations arose at once. The inventor had foreseen this issue and
was optimistic. Thereupon the authorities asked if the inventor were
prepared to justify his claims. The retort was positive. Forthwith the
Junkers decided to submit it to the test.
This ship is of quite a distinctive type. It is an aerial cruiser, and
the inventor claims that it combines all the essential qualifications
of the Zeppelin and of the competitors of the latter, in addition to the
advantage of being capable of dissection, transportation in parts, and
rapid re-erection at any desired spot. The length of the vessel is about
270 feet; maximum diameter approximately 42 feet, and capacity about
300,000 cubic feet. The outstanding feature is a rigid keel-frame
forming a covered passage way below the envelope or gas-bag, combined
with easy access to all parts of the craft while under way, together
with an artificial stiffening which dispenses with the necessity of
attaching any additional cars. The frame is so designed that the load,
as well as the ballast and fuel tanks, may be distributed as desired,
and at the same time it ensures an advantageous disposition of the
steering mechanism, far removed from the centre of rotation at the
stern, without any overloading of the latter.
The lifting part of the airship comprises a single gas bag fitted with
two ballonets provided to ensure the requisite gas-tension in the main
envelope, while at the same time permitting, in times of emergency,
a rapid change of altitude. Self-contained blowers contribute to the
preservation of the shape of the envelope, the blowers and the ballonets
being under the control of the pilot. Planes resembling Venetian blinds
facilitate vertical steering, while the suspension of the keel is
carried out in such a manner as to secure uniformity of weight upon the
gas bag. The propelling power comprises two sets of internal combustion
engines, each developing 130 horse-power, the transmission being through
rubber belting. The propellers, built of wood, make 350 revolutions per
minute, and are set as closely as possible to the centre of resistance.
But the most salient characteristic of this machine is its portability.
It can be dismantled and transported by wagons to any desired spot,
the suspension frame being constructed in units, each of which is
sufficiently small to be accommodated in an ordinary vehicle. Upon
arrival the parts may be put together speedily and easily. The
authorities submitted the airship to exacting trials and were so
impressed by its characteristics and the claims of the inventor that
undoubtedly it will be brought into service during the present crisis.
At the same time the whole faith of the German military staff so far
as airship operations are concerned, is pinned to the Zeppelin.
Notwithstanding its many drawbacks it is the vessel which will be used
for the invasion of Great Britain. Even the harbour question, which is
admitted to be somewhat acute, has been solved to a certain degree.
At strategical points permanent harbours or airship sheds have been
established. Seeing that the airships demand considerable skill in
docking and undocking, and that it is impossible to achieve these
operations against the wind, swinging sheds have been adopted.
On water the practice is to anchor a floating harbour at one end,
leaving the structure to swing round with the wind. But on dry land such
a dock is impossible. Accordingly turntable sheds have been adopted.
The shed is mounted upon a double turn-table, there being two circular
tracks the one near the centre of the shed and the other towards its
extremities. The shed is mounted upon a centre pivot and wheels engaged
with these inner and outer tracks. In this manner the shed may be swung
round to the most favourable point of the compass according to the wind.
In the field, however, such practices are impossible, and the issue
in this connection has been overcome by recourse to what may be termed
portable harbours. They resemble the tents of peripatetic circuses and
travelling exhibitions. There is a network of vertical steel members
which may be set with facility and speed and which are stayed by
means of wire guys. At the top of the outer vertical posts pulleys
are provided whereby the outer skin or canvas forming the walls may
be hauled into position, while at the apex of the roof further pulleys
ensure the proper placing of the roofing. The airship is able to enter
or leave from either end according to conditions. The material is
fireproofed as a precautionary measure, but at the same time the modern
aerial bomb is able to penetrate the roofing without any difficulty and
to explode against the airship anchored within.
The one great objection to the Zeppelin harbour is the huge target it
offers to hostile attack, which, in the event of a vessel being moored
within, is inevitably serious. Thus, for instance, upon the occasion of
the air raids conducted by Lieutenant Collet and of Squadron
Commander Briggs and his colleagues at Dusseldorf and Friedrichshafen
respectively, little difficulty was experienced in destroying the
airships riding at anchor. The target offered by the shed is so
extensive that it would be scarcely possible for a flying enemy to miss
it. A bomb dropped from a reasonable height, say 500 feet, would be
almost certain to strike some part of the building, and a Zeppelin is
an easy vessel to destroy. The firing of one balloon is sufficient
to detonate the whole, for the simple reason that hydrogen gas is
continuously oozing through the bags in which it is contained. According
to a recent statement the Germans are said to be utilising an inert
or non-inflammable gas, equal in lifting power to hydrogen, for the
inflation of military craft, but scientific thought does not entertain
this statement with any degree of seriousness. No gas as light as
hydrogen and non-explosive is known to commerce.
Will Germany invade Great Britain by air? This is the absorbing topic of
the moment--one which has created intense interest and a certain feeling
of alarm among the timorous. Although sporadic raids are considered
to be possible and likely to be carried out with a varying measure
of success--such as that made upon the British East Coast--eminent
authorities ridicule an invasion in force. The risk would be enormous,
although there is no doubt that Germany, which has always maintained
that an invasion of this character will be made, will be compelled to
essay such a task, in order to satisfy public opinion, and to justify
official statements. It is a moot point, however, whether the invaders
ever will succeed in making good their escape, unless Nature proves
exceptionally kind.
The situation is best summed up in the unbiassed report of General
George P. Scriven, Chief Signal officer of the United States Army to the
U.S. Secretary of War. In this report, which deals exhaustively with the
history, construction and achievements of airships, such an invasion
is described as fantastic and impracticable. Writing on November 10th,
1914, the officer declares that "he is not prepared to recommend
the American Army to take up seriously the question of constructing
dirigibles, as they are not worth their cost as offensive machines,
while for reconnaissance or defence they are of far less value than
aeroplanes." In his words, "Dirigibles are seemingly useless in defence
against the aeroplane or gun-fire."
In order to be able to make an invasion in force upon Great Britain's
cities extremely favourable weather must prevail, and the treacherous
nature of the weather conditions of the North Sea are known fully well
both to British and Teuton navigators. Seeing that the majority of the
Zeppelin pilots are drawn from the Navy and mercantile marine, and
thus are conversant with the peculiarities and characteristics of
this stretch of salt water, it is only logical to suppose that their
knowledge will exert a powerful influence in any such decision, the
recommendations of the meteorological savants not withstanding.
When the Zeppelin pride of the German Navy "L-1" was hurled to
destruction by a typical North Sea squall, Captain Blew of the Victoria
Luise, a Zeppelin with many great achievements to her credit, whose
navigator was formerly in the Navy, and thus is familiar with the whole
issue, explained that this atmospheric liveliness of the North Sea
prevails for the most part in the latitude of Norway, but that it
frequently extends as far south as the gate of the Channel. He related
furthermore that the rain squalls are of tropical violence, while the
vertical thrusts of air are such that no dirigible as yet constructed
could ever hope to live in them. Under such conditions, he continued,
the gas is certain to cool intensely, and the hull must then become
waterlogged, not to mention the downward thrust of the rain. Under such
conditions buoyancy must be imperilled to such a degree as to demand the
jettisoning of every piece of ballast, fuel and other removable weight,
including even the steadying and vertical planes. When this has been
done, he pointed out, nothing is left with which to combat the upward
vertical thrusts of the air. To attempt to run before the wind is to
court positive disaster, as the wind is certain to gain the mastery.
Once the airship loses steering way and is rendered uncontrollable it
becomes the sport of the forces of Nature, with the result that
destruction is merely a matter of minutes, or even seconds.
Every navigator who knows the North Sea will support these conclusions.
Squalls and blizzards in winter, and thunderstorms in summer, rise
with startling suddenness and rage with terrific destructive fury.
Such conditions must react against the attempt of an aerial invasion
in force, unless it be made in the character of the last throw by a
desperate gambler, with good fortune favouring the dash to a certain
degree. But lesser and more insignificant Zeppelin raids are likely
to be somewhat frequent, and to be made at every favourable climatic
opportunity.