AEROSTATICS
I
BEGINNINGS
Francesco Lana, with his ‘aerial ship’ stands as one of the first
great exponents of aerostatics; up to the time of the Mongolfier and
Charles balloon experiments, aerostatic and aerodynamic research
are so inextricably intermingled that it has been thought well to
treat of them as one, and thus the work of Lana, Veranzio and his
parachute, Guzman’s frauds, and the like, have already been sketched.
In connection with Guzman, Hildebrandt states in his _Airships Past
and Present_, a fairly exhaustive treatise on the subject up to
1906, the year of its publication, that there were two inventors--or
charlatans--Lorenzo de Guzman and a monk Bartolemeo Laurenzo, the
former of whom constructed an unsuccessful airship out of a wooden
basket covered with paper, while the latter made certain experiments
with a machine of which no description remains. A third de Guzman,
some twenty-five years later, announced that he had constructed a
flying machine, with which he proposed to fly from a tower to prove
his success to the public. The lack of record of any fatal accident
overtaking him about that time seems to show that the experiment was
not carried out.
Galien, a French monk, published a book _L’art de naviguer dans l’air_
in 1757, in which it was conjectured that the air at high levels was
lighter than that immediately over the surface of the earth. Galien
proposed to bring down the upper layers of air and with them fill a
vessel, which by Archimidean principle would rise through the heavier
atmosphere. If one went high enough, said Galien, the air would be two
thousand times as light as water, and it would be possible to construct
an airship, with this light air as lifting factor, which should be as
large as the town of Avignon, and carry four million passengers with
their baggage. How this high air was to be obtained is matter for
conjecture--Galien seems to have thought in a vicious circle, in which
the vessel that must rise to obtain the light air must first be filled
with it in order to rise.
Cavendish’s discovery of hydrogen in 1776 set men thinking, and soon a
certain Doctor Black was suggesting that vessels might be filled with
hydrogen, in order that they might rise in the air. Black, however,
did not get beyond suggestion; it was Leo Cavallo who first made
experiments with hydrogen, beginning with filling soap bubbles, and
passing on to bladders and special paper bags. In these latter the gas
escaped, and Cavallo was about to try goldbeaters’ skin at the time
that the Mongolfiers came into the field with their hot air balloon.
Joseph and Stephen Mongolfier, sons of a wealthy French paper
manufacturer, carried out many experiments in physics, and Joseph
interested himself in the study of aeronautics some time before the
first balloon was constructed by the brothers--he is said to have made
a parachute descent from the roof of his house as early as 1771, but
of this there is no proof. Galien’s idea, together with study of the
movement of clouds, gave Joseph some hope of achieving aerostation
through Galien’s schemes, and the first experiments were made by
passing steam into a receiver, which, of course, tended to rise--but
the rapid condensation of the steam prevented the receiver from more
than threatening ascent. The experiments were continued with smoke,
which produced only a slightly better effect, and, moreover, the paper
bag into which the smoke was induced permitted of escape through its
pores; finding this method a failure the brothers desisted until
Priestley’s work became known to them, and they conceived the use of
hydrogen as a lifting factor. Trying this with paper bags, they found
that the hydrogen escaped through the pores of the paper.
Their first balloon, made of paper, reverted to the hot-air principle;
they lighted a fire of wool and wet straw under the balloon--and as a
matter of course the balloon took fire after very little experiment;
thereupon they constructed a second, having a capacity of 700 cubic
feet, and this rose to a height of over 1,000 feet. Such a success gave
them confidence, and they gave their first public exhibition on June
5th, 1783, with a balloon constructed of paper and of a circumference
of 112 feet. A fire was lighted under this balloon, which, after rising
to a height of 1,000 feet, descended through the cooling of the air
inside a matter of ten minutes. At this the Académie des Sciences
invited the brothers to conduct experiments in Paris.
The Mongolfiers were undoubtedly first to send up balloons, but other
experimenters were not far behind them, and before they could get to
Paris in response to their invitation, Charles, a prominent physicist
of those days, had constructed a balloon of silk, which he proofed
against escape of gas with rubber--the Roberts had just succeeded in
dissolving this substance to permit of making a suitable coating for
the silk. With a quarter of a ton of sulphuric acid, and half a ton
of iron filings and turnings, sufficient hydrogen was generated in
four days to fill Charles’s balloon, which went up on August 29th,
1783. Although the day was wet, Paris turned out to the number of over
300,000 in the Champs de Mars, and cannon were fired to announce the
ascent of the balloon. This, rising very rapidly, disappeared amid the
rain clouds, but, probably bursting through no outlet being provided
to compensate for the escape of gas, fell soon in the neighbourhood of
Paris. Here peasants, ascribing evil supernatural influence to the fall
of such a thing from nowhere, went at it with the implements of their
craft--forks, hoes, and the like--and maltreated it severely, finally
attaching it to a horse’s tail and dragging it about until it was mere
rag and scrap.
Meanwhile, Joseph Mongolfier, having come to Paris, set about the
construction of a balloon out of linen; this was in three diverse
sections, the top being a cone 30 feet in depth, the middle a cylinder
42 feet in diameter by 26 feet in depth, and the bottom another cone
20 feet in depth from junction with the cylindrical portion to its
point. The balloon was both lined and covered with paper, decorated in
blue and gold. Before ever an ascent could be attempted this ambitious
balloon was caught in a heavy rainstorm which reduced its paper
covering to pulp and tore the linen at its seams, so that a supervening
strong wind tore the whole thing to shreds.
Mongolfier’s next balloon was spherical, having a capacity of 52,000
cubic feet. It was made from water-proofed linen, and on September
19th, 1783, it made an ascent for the palace courtyard at Versailles,
taking up as passengers a cock, a sheep, and a duck. A rent at the top
of the balloon caused it to descend within eight minutes, and the duck
and sheep were found none the worse for being the first living things
to leave the earth in a balloon, but the cock, evidently suffering, was
thought to have been affected by the rarefaction of the atmosphere at
the tremendous height reached--for at that time the general opinion was
that the atmosphere did not extend more than four or five miles above
the earth’s surface. It transpired later that the sheep had trampled on
the cock, causing more solid injury than any that might be inflicted by
rarefied air in an eight-minute ascent and descent of a balloon.
For achieving this flight Joseph Mongolfier received from the King
of France a pension of £40, while Stephen was given the Order of St
Michael, and a patent of nobility was granted to their father. They
were made members of the Legion d’Honneur, and a scientific deputation,
of which Faujas de Saint-Fond, who had raised the funds with which
Charles’s hydrogen balloon was constructed, presented to Stephen
Mongolfier a gold medal struck in honour of his aerial conquest.
Since Joseph appears to have had quite as much share in the success
as Stephen, the presentation of the medal to one brother only was in
questionable taste, unless it was intended to balance Joseph’s pension.
Once aerostation had been proved possible, many people began the
construction of small balloons--the whole thing was regarded as a
matter of spectacles and as a form of amusement by the great majority.
A certain Baron de Beaumanoir made the first balloon of goldbeaters’
skin, this being eighteen inches in diameter, and using hydrogen as a
lifting factor. Few people saw any possibilities in aerostation, in
spite of the adventures of the duck and sheep and cock; voyages to
the moon were talked and written, and there was more of levity than
seriousness over ballooning as a rule. The classic retort of Benjamin
Franklin stands as an exception to the general rule: asked what was the
use of ballooning--‘What’s the use of a baby?’ he countered, and the
spirit of that reply brought both the dirigible and the aeroplane to
being, later.
The next noteworthy balloon was one by Stephen Mongolfier, designed
to take up passengers, and therefore of rather large dimensions, as
these things went then. The capacity was 100,000 cubic feet, the depth
being 85 feet, and the exterior was very gaily decorated. A short,
cylindrical opening was made at the lower extremity, and under this
a fire-pan was suspended, above the passenger car of the balloon.
On October 15th, 1783, Pilatre de Rozier made the first balloon
ascent--but the balloon was held captive, and only allowed to rise to
a height of 80 feet. But, a little later in 1783, Rozier secured the
honour of making the first ascent in a free balloon, taking up with
him the Marquis d’Arlandes. It had been originally intended that two
criminals, condemned to death, should risk their lives in the perilous
venture, with the prospect of a free pardon if they made a safe
descent, but d’Arlandes got the royal consent to accompany Rozier, and
the criminals lost their chance. Rozier and d’Arlandes made a voyage
lasting for twenty-five minutes, and, on landing, the balloon collapsed
with such rapidity as almost to suffocate Rozier, who, however, was
dragged out to safety by d’Arlandes. This first aerostatic journey took
place on November 21st, 1783.
Some seven months later, on June 4th, 1784, a Madame Thible ascended
in a free balloon, reaching a height of 9,000 feet, and making a
journey which lasted for forty-five minutes--the great King Gustavus
of Sweden witnessed this ascent. France grew used to balloon ascents
in the course of a few months, in spite of the brewing of such a storm
as might have been calculated to wipe out all but purely political
interests. Meanwhile, interest in the new discovery spread across the
Channel, and on September 15th, 1784, one Vincent Lunardi made the
first balloon voyage in England, starting from the Artillery Ground at
Chelsea, with a cat and dog as passengers, and landing in a field in
the parish of Standon, near Ware. There is a rather rare book which
gives a very detailed account of this first ascent in England, one
copy of which is in the library of the Royal Aeronautical Society; the
venturesome Lunardi won a greater measure of fame through his exploit
than did Cody for his infinitely more courageous and--from a scientific
point of view--valuable first aeroplane ascent in this country.
The Mongolfier type of balloon, depending on hot air for its lifting
power, was soon realised as having dangerous limitations. There was
always a possibility of the balloon catching fire while it was being
filled, and on landing there was further danger from the hot pan
which kept up the supply of hot air on the voyage--the collapsing
balloon fell on the pan, inevitably. The scientist Saussure, observing
the filling of the balloons very carefully, ascertained that it was
rarefaction of the air which was responsible for the lifting power,
and not the heat in itself, and, owing to the rarefaction of the air
at normal temperature at great heights above the earth, the limit of
ascent for a balloon of the Mongolfier type was estimated by him at
under 9,000 feet. Moreover, since the amount of fuel that could be
carried for maintaining the heat of the balloon after inflation was
subject to definite limits, prescribed by the carrying capacity of the
balloon, the duration of the journey was necessarily limited just as
strictly.
These considerations tended to turn the minds of those interested
in aerostation to consideration of the hydrogen balloon evolved by
Professor Charles. Certain improvements had been made by Charles
since his first construction; he employed rubber-coated silk in the
construction of a balloon of 30 feet diameter, and provided a net for
distributing the pressure uniformly over the surface of the envelope;
this net covered the top half of the balloon, and from its lower edge
dependent ropes hung to join on a wooden ring, from which the car of
the balloon was suspended--apart from the extension of the net so as to
cover in the whole of the envelope, the spherical balloon of to-day is
virtually identical with that of Charles in its method of construction.
He introduced the valve at the top of the balloon, by which escape of
gas could be controlled, operating his valve by means of ropes which
depended to the car of the balloon, and he also inserted a tube, of
about 7 inches diameter, at the bottom of the balloon, not only for
purposes of inflation, but also to provide a means of escape for gas in
case of expansion due to atmospheric conditions.
Sulphuric acid and iron filings were used by Charles for filling his
balloon, which required three days and three nights for the generation
of its 14,000 cubic feet of hydrogen gas. The inflation was completed
on December 1st, 1783, and the fittings carried included a barometer
and a grapnel form of anchor. In addition to this, Charles provided
the first ‘ballon sondé’ in the form of a small pilot balloon which
he handed to Mongolfier to launch before his own ascent, in order to
determine the direction and velocity of the wind. It was a graceful
compliment to his rival, and indicated that, although they were both
working to the one end, their rivalry was not a matter of bitterness.
Ascending on December 1st, 1783, Charles took with him one of the
brothers Robert, and with him made the record journey up to that date,
covering a period of three and three-quarter hours, in which time they
journeyed some forty miles. Robert then landed, and Charles ascended
again alone, reaching such a height as to feel the effects of the
rarefaction of the air, this very largely due to the rapidity of his
ascent. Opening the valve at the top of the balloon, he descended
thirty-five minutes after leaving Robert behind, and came to earth a
few miles from the point of the first descent. His discomfort over the
rapid ascent was mainly due to the fact that, when Robert landed, he
forgot to compensate for the reduction of weight by taking in further
ballast, but the ascent proved the value of the tube at the bottom of
the balloon envelope, for the gas escaped very rapidly in that second
ascent, and, but for the tube, the balloon must inevitably have burst
in the air, with fatal results for Charles.
As in the case of aeroplane flight, as soon as the balloon was
proved practicable the flight across the English Channel was talked
of, and Rozier, who had the honour of the first flight, announced his
intention of being first to cross. But Blanchard, who had an idea
for a ‘flying car,’ anticipated him, and made a start from Dover on
January 7th, 1785, taking with him an American doctor named Jeffries.
Blanchard fitted out his craft for the journey very thoroughly, taking
provisions, oars, and even wings, for propulsion in case of need. He
took so much, in fact, that as soon as the balloon lifted clear of the
ground the whole of the ballast had to be jettisoned, lest the balloon
should drop into the sea. Half-way across the Channel the sinking of
the balloon warned Blanchard that he had to part with more than ballast
to accomplish the journey, and all the equipment went, together with
certain books and papers that were on board the car. The balloon looked
perilously like collapsing, and both Blanchard and Jeffries began to
undress in order further to lighten their craft--Jeffries even proposed
a heroic dive to save the situation, but suddenly the balloon rose
sufficiently to clear the French coast, and the two voyagers landed at
a point near Calais in the Forest of Guines, where a marble column was
subsequently erected to commemorate the great feat.
Rozier, although not first across, determined to be second, and for
that purpose he constructed a balloon which was to owe its buoyancy
to a combination of the hydrogen and hot air principles. There was
a spherical hydrogen balloon above, and beneath it a cylindrical
container which could be filled with hot air, thus compensating for the
leakage of gas from the hydrogen portion of the balloon--regulating the
heat of his fire, he thought, would give him perfect control in the
matter of ascending and descending.
On July 16th, 1785, a favourable breeze gave Rozier his opportunity of
starting from the French coast, and with a passenger aboard he cast
off in his balloon, which he had named the ‘Aero-Mongolfiere.’ There
was a rapid rise at first, and then for a time the balloon remained
stationary over the land, after which a cloud suddenly appeared round
the balloon, denoting that an explosion had taken place. Both Rozier
and his companion were killed in the fall, so that he, first to leave
the earth by balloon, was also first victim to the art of aerostation.
There followed, naturally, a lull in the enthusiasm with which
ballooning had been taken up, so far as France was concerned. In Italy,
however, Count Zambeccari took up hot-air ballooning, using a spirit
lamp to give him buoyancy, and on the first occasion when the balloon
car was set on fire Zambeccari let down his passenger by means of the
anchor rope, and managed to extinguish the fire while in the air. This
reduced the buoyancy of the balloon to such an extent that it fell
into the Adriatic and was totally wrecked, Zambeccari being rescued by
fishermen. He continued to experiment up to 1812, when he attempted to
ascend at Bologna; the spirit in his lamp was upset by the collision
of the car with a tree, and the car was again set on fire. Zambeccari
jumped from the car when it was over fifty feet above level ground, and
was killed. With him the Rozier type of balloon, combining the hydrogen
and hot air principles, disappeared; the combination was obviously too
dangerous to be practical.
The brothers Robert were first to note how the heat of the sun
acted on the gases within a balloon envelope, and it has since been
ascertained that sun rays will heat the gas in a balloon to as much
as 80 degrees Fahrenheit greater temperature than the surrounding
atmosphere; hydrogen, being less affected by change of temperature than
coal gas, is the most suitable filling element, and coal gas comes next
as the medium of buoyancy. This for the free and non-navigable balloon,
though for the airship, carrying means of combustion, and in military
work liable to ignition by explosives, the gas helium seems likely to
replace hydrogen, being non-combustible.
In spite of the development of the dirigible airship, there remains
work for the free, spherical type of balloon in the scientific field.
Blanchard’s companion on the first Channel crossing by balloon, Dr
Jeffries, was the first balloonist to ascend for purely scientific
purposes; as early as 1784 he made an ascent to a height of 9,000 feet,
and observed a fall in temperature of from 51 degrees--at the level
of London, where he began his ascent--to 29 degrees at the maximum
height reached. He took up an electrometer, a hydrometer, a compass, a
thermometer, and a Toricelli barometer, together with bottles of water,
in order to collect samples of the air at different heights. In 1785 he
made a second ascent, when trigonometrical observations of the height
of the balloon were made from the French coast, giving an altitude of
4,800 feet.
The matter was taken up on its scientific side very early in America,
experiments in Philadelphia being almost simultaneous with those of the
Mongolfiers in France. The flight of Rozier and d’Arlandes inspired
two members of the Philadelphia Philosophical Academy to construct a
balloon or series of balloons of their own design; they made a machine
which consisted of no less than 47 small hydrogen balloons attached
to a wicker car, and made certain preliminary trials, using animals
as passengers. This was followed by a captive ascent with a man as
passenger, and eventually by the first free ascent in America, which
was undertaken by one James Wilcox, a carpenter, on December 28th 1783.
Wilcox, fearful of falling into a river, attempted to regulate his
landing by cutting slits in some of the supporting balloons, which was
the method adopted for regulating ascent or descent in this machine.
He first cut three, and then, finding that the effect produced was not
sufficient, cut three more, and then another five--eleven out of the
forty-seven. The result was so swift a descent that he dislocated his
wrist on landing.
A NOTE ON BALLONETS OR AIR BAGS.
Meusnier, toward the end of the eighteenth century, was first to
conceive the idea of compensating for the loss of gas due to expansion
by fitting to the interior of a free balloon a ballonet, or air bag,
which could be pumped full of air so as to retain the shape and
rigidity of the envelope.
The ballonet became particularly valuable as soon as airship
construction became general, and it was in the course of advance in
Astra Torres design that the project was introduced of using the
ballonets in order to give inclination from the horizontal. In the
earlier Astra Torres, trimming was accomplished by moving the car fore
and aft--this in itself was an advance on the separate ‘sliding weight’
principle--and this was the method followed in the Astra Torres bought
by the British Government from France in 1912 for training airship
pilots. Subsequently, the two ballonets fitted inside the envelope were
made to serve for trimming by the extent of their inflation, and this
method of securing inclination proved the best until exterior rudders,
and greater engine power, supplanted it, as in the Zeppelin and, in
fact, all rigid types.
In the kite balloon, the ballonet serves the purpose of a rudder,
filling itself through the opening being kept pointed toward the
wind--there is an ingenious type of air scoop with non-return valve
which assures perfect inflation. In the S. S. type of airship, two
ballonets are provided, the supply of air being taken from the
propeller draught by a slanting aluminium tube to the underside of the
envelope, where it meets a longitudinal fabric hose which connects the
two ballonet air inlets. In this hose the non-return air valves, known
as ‘crab-pots,’ are fitted, on either side of the junction with the
air-scoop. Two automatic air valves, one for each ballonet, are fitted
in the underside of the envelope, and, as the air pressure tends to
open these instead of keeping them shut, the spring of the valve is set
inside the envelope. Each spring is set to open at a pressure of 25 to
28 mm.
II
THE FIRST DIRIGIBLES
Having got off the earth, the very early balloonists set about the task
of finding a means of navigating the air, but, lacking steam or other
accessory power to human muscle, they failed to solve the problem.
Joseph Mongolfier speedily exploded the idea of propelling a balloon
either by means of oars or sails, pointing out that even in a dead
calm a speed of five miles an hour would be the limit achieved. Still,
sailing balloons were constructed, even up to the time of Andree, the
explorer, who proposed to retard the speed of the balloon by ropes
dragging on the ground, and then to spread a sail which should catch
the wind and permit of deviation of the course. It has been proved that
slight divergences from the course of the wind can be obtained by this
means, but no real navigation of the air could be thus accomplished.
Professor Wellner, of Brunn, brought up the idea of a sailing balloon
in more practical fashion in 1883. He observed that surfaces inclined
to the horizontal have a slight lateral motion in rising and falling,
and deduced that by alternate lowering and raising of such surfaces
he would be able to navigate the air, regulating ascent and descent
by increasing or decreasing the temperature of his buoyant medium in
the balloon. He calculated that a balloon, 50 feet in diameter and
150 feet in length, with a vertical surface in front and a horizontal
surface behind, might be navigated at a speed of ten miles per hour,
and in actual tests at Brunn he proved that a single rise and fall
moved the balloon three miles against the wind. His ideas were further
developed by Lebaudy in the construction of the early French dirigibles.
According to Hildebrandt,[11] the first sailing balloon was built in
1784 by Guyot, who made his balloon egg-shaped, with the smaller end
at the back and the longer axis horizontal; oars were intended to
propel the craft, and naturally it was a failure. Carra proposed the
use of paddle wheels, a step in the right direction, by mounting them
on the sides of the car, but the improvement was only slight. Guyton
de Morveau, entrusted by the Academy of Dijon with the building of a
sailing balloon, first used a vertical rudder at the rear end of his
construction--it survives in the modern dirigible. His construction
included sails and oars, but, lacking steam or other than human
propulsive power, the airship was a failure equally with Guyot’s.
Two priests, Miollan and Janinet, proposed to drive balloons through
the air by the forcible expulsion of the hot air in the envelope
from the rear of the balloon. An opening was made about half-way
up the envelope, through which the hot air was to escape, buoyancy
being maintained by a pan of combustibles in the car. Unfortunately,
this development of the Mongolfier type never got a trial, for those
who were to be spectators of the first flight grew exasperated at
successive delays, and in the end, thinking that the balloon would
never rise, they destroyed it.
Meusnier, a French general, first conceived the idea of compensating
for loss of gas by carrying an air bag inside the balloon, in order
to maintain the full expansion of the envelope. The brothers Robert
constructed the first balloon in which this was tried, and placed the
air bag near the neck of the balloon, which was intended to be driven
by oars, and steered by a rudder. A violent swirl of wind which was
encountered on the first ascent tore away the oars and rudder and broke
the ropes which held the air bag in position; the bag fell into the
opening of the neck and stopped it up, preventing the escape of gas
under expansion. The Duc de Chartres, who was aboard, realised the
extreme danger of the envelope bursting as the balloon ascended, and
at 16,000 feet he thrust a staff through the envelope--another account
says that he slit it with his sword--and thus prevented disaster. The
descent after this rip in the fabric was swift, but the passengers got
off without injury in the landing.
Meusnier, experimenting in various ways, experimented with regard to
the resistance offered by various shapes to the air, and found that an
elliptical shape was best; he proposed to make the car boat-shaped, in
order further to decrease the resistance, and he advocated an entirely
rigid connection between the car and the body of the balloon, as
indispensable to a dirigible.[12] He suggested using three propellers,
which were to be driven by hand by means of pulleys, and calculated
that a crew of eighty would be required to furnish sufficient motive
power. Horizontal fins were to be used to assure stability, and
Meusnier thoroughly investigated the pressures exerted by gases,
in order to ascertain the stresses to which the envelope would be
subjected. More important still, he went into detail with regard to
the use of air bags, in order to retain the shape of the balloon under
varying pressures of gas due to expansion and consequent losses; he
proposed two separate envelopes, the inner one containing gas, and the
space between it and the outer one being filled with air. Further,
by compressing the air inside the air bag, the rate of ascent or
descent could be regulated. Lebaudy, acting on this principle, found
it possible to pump air at the rate of 35 cubic feet per second, thus
making good loss of ballast which had to be thrown overboard.
Meusnier’s balloon, of course, was never constructed, but his ideas
have been of value to aerostation up to the present time. His career
ended in the revolutionary army in 1793, when he was killed in the
fighting before Mayence, and the King of Prussia ordered all firing
to cease until Meusnier had been buried. No other genius came forward
to carry on his work, and it was realised that human muscle could not
drive a balloon with certainty through the air; experiment in this
direction was abandoned for nearly sixty years, until in 1852 Giffard
brought the first practicable power-driven dirigible to being.
Giffard, inventor of the steam injector, had already made balloon
ascents when he turned to aeronautical propulsion, and constructed a
steam engine of 5 horse-power with a weight of only 100 lbs.--a great
achievement for his day. Having got his engine, he set about making
the balloon which it was to drive; this he built with the aid of two
other enthusiasts, diverging from Meusnier’s ideas by making the ends
pointed, and keeping the body narrowed from Meusnier’s ellipse to a
shape more resembling a rather fat cigar. The length was 144 feet, and
the greatest diameter only 40 feet, while the capacity was 88,000 cubic
feet. A net which covered the envelope of the balloon supported a spar,
66 feet in length, at the end of which a triangular sail was placed
vertically to act as rudder. The car, slung 20 feet below the spar,
carried the engine and propeller. Engine and boiler together weighed
350 lbs., and drove the 11 foot propeller at 110 revolutions per minute.
As precaution against explosion, Giffard arranged wire gauze in front
of the stoke-hole of his boiler, and provided an exhaust pipe which
discharged the waste gases from the engine in a downward direction.
With this first dirigible he attained to a speed of between 6 and 8
feet per second, thus proving that the propulsion of a balloon was a
possibility, now that steam had come to supplement human effort.
Three years later he built a second dirigible, reducing the diameter
and increasing the length of the gas envelope, with a view to reducing
air resistance. The length of this was 230 feet, the diameter only 33
feet, and the capacity was 113,000 cubic feet, while the upper part of
the envelope, to which the covering net was attached, was specially
covered to ensure a stiffening effect. The car of this dirigible was
dropped rather lower than that of the first machine, in order to
provide more thoroughly against the danger of explosions. Giffard, with
a companion named Yon as passenger, took a trial trip on this vessel,
and made a journey against the wind, though slowly. In commencing to
descend, the nose of the envelope tilted upwards, and the weight of
the car and its contents caused the net to slip, so that just before
the dirigible reached the ground, the envelope burst. Both Giffard and
his companion escaped with very slight injuries.
Plans were immediately made for the construction of a third dirigible,
which was to be 1,970 feet in length, 98 feet in extreme diameter, and
to have a capacity of 7,800,000 cubic feet of gas. The engine of this
giant was to have weighed 30 tons, and with it Giffard expected to
attain a speed of 40 miles per hour. Cost prevented the scheme being
carried out, and Giffard went on designing small steam engines until
his invention of the steam injector gave him the funds to turn to
dirigibles again. He built a captive balloon for the great exhibition
in London in 1868, at a cost of nearly £30,000, and designed a
dirigible balloon which was to have held a million and three-quarters
cubic feet of gas, carry two boilers, and cost about £40,000. The plans
were thoroughly worked out, down to the last detail, but the dirigible
was never constructed. Giffard went blind, and died in 1882--he stands
as the great pioneer of dirigible construction, more on the strength of
the two vessels which he actually built than on that of the ambitious
later conceptions of his brain.
In 1872 Dupuy de Lome, commissioned by the French government, built a
dirigible which he proposed to drive by man-power--it was anticipated
that the vessel would be of use in the siege of Paris, but it was not
actually tested till after the conclusion of the war. The length of
this vessel was 118 feet, its greatest diameter 49 feet, the ends being
pointed, and the motive power was by a propeller which was revolved by
the efforts of eight men. The vessel attained to about the same speed
as Giffard’s steam-driven airship; it was capable of carrying fourteen
men, who, apart from these engaged in driving the propeller, had to
manipulate the pumps which controlled the air bags inside the gas
envelope.
In the same year Paul Haenlein, working in Vienna, produced an airship
which was a direct forerunner of the Lebaudy type, 164 feet in length,
30 feet greatest diameter, and with a cubic capacity of 85,000 feet.
Semi-rigidity was attained by placing the car as close to the envelope
as possible, suspending it by crossed ropes, and the motive power was
a gas engine of the Lenoir type, having four horizontal cylinders, and
giving about 5 horse-power with a consumption of about 250 cubic feet
of gas per hour. This gas was sucked from the envelope of the balloon,
which was kept fully inflated by pumping in compensating air to the
air bags inside the main envelope. A propeller, 15 feet in diameter,
was driven by the Lenoir engine at 40 revolutions per minute. This
was the first instance of the use of an internal combustion engine in
connection with aeronautical experiments.
The envelope of this dirigible was rendered airtight by means of
internal rubber coating, with a thinner film on the outside. Coal gas,
used for inflation, formed a suitable fuel for the engine, but limited
the height to which the dirigible could ascend. Such trials as were
made were carried out with the dirigible held captive, and a speed of
15 feet per second was attained. Full experiment was prevented through
funds running low, but Haenlein’s work constituted a distinct advance
on all that had been done previously.
Two brothers, Albert and Gaston Tissandier, were next to enter the
field of dirigible construction; they had experimented with balloons
during the Franco-Prussian War, and had attempted to get into Paris by
balloon during the siege, but it was not until 1882 that they produced
their dirigible.
This was 92 feet in length and 32 feet in greatest diameter, with
a cubic capacity of 37,500 feet, and the fabric used was varnished
cambric. The car was made of bamboo rods, and in addition to its crew
of three, it carried a Siemens dynamo, with 24 bichromate cells, each
of which weighed 17 lbs. The motor gave out 1½ horse-power, which was
sufficient to drive the vessel at a speed of up to 10 feet per second.
This was not so good as Haenlein’s previous attempt and, after £2,000
had been spent, the Tissandiers abandoned their experiments, since a
5-mile breeze was sufficient to nullify the power of the motor.
Renard, a French officer who had studied the problem of dirigible
construction since 1878, associated himself first with a brother
officer named La Haye, and subsequently with another officer, Krebs, in
the construction of the second dirigible to be electrically-propelled.
La Haye first approached Colonel Laussedat, in charge of the Engineers
of the French Army, with a view to obtaining funds, but was refused,
in consequence of the practical failure of all experiments since 1870.
Renard, with whom Krebs had now associated himself, thereupon went to
Gambetta, and succeeded in getting a promise of a grant of £8,000 for
the work; with this promise Renard and Krebs set to work.
They built their airship in torpedo shape, 165 feet in length, and of
just over 27 feet greatest diameter--the greatest diameter was at the
front, and the cubic capacity was 66,000 feet. The car itself was 108
feet in length, and 4½ feet broad, covered with silk over the bamboo
framework. The 23 foot diameter propeller was of wood, and was driven
by an electric motor connected to an accumulator, and yielding 8.5
horse-power. The sweep of the propeller, which might have brought it
in contact with the ground in landing, was counteracted by rendering
it possible to raise the axis on which the blades were mounted,
and a guide rope was used to obviate damage altogether, in case of
rapid descent. There was also a ‘sliding weight’ which was movable
to any required position to shift the centre of gravity as desired.
Altogether, with passengers and ballast aboard, the craft weighed two
tons.
In the afternoon of August 9th, 1884, Renard and Krebs ascended in
the dirigible--which they had named ‘La France,’ from the military
ballooning ground at Chalais-Meudon, making a circular flight of about
five miles, the latter part of which was in the face of a slight
wind. They found that the vessel answered well to her rudder, and the
five-mile flight was made successfully in a period of 23 minutes.
Subsequent experimental flights determined that the air speed of the
dirigible was no less than 14½ miles per hour, by far the best that
had so far been accomplished in dirigible flight. Seven flights in all
were made, and of these five were completely successful, the dirigible
returning to its starting point with no difficulty. On the other two
flights it had to be towed back.
Renard attempted to repeat his construction on a larger scale, but
funds would not permit, and the type was abandoned; the motive power
was not sufficient to permit of more than short flights, and even to
the present time electric motors, with their necessary accumulators,
are far too cumbrous to compete with the self-contained internal
combustion engine. France had to wait for the Lebaudy brothers, just as
Germany had to wait for Zeppelin and Parseval.
Two German experimenters, Baumgarten and Wolfert, fitted a Daimler
motor to a dirigible balloon which made its first ascent at Leipzig in
1880. This vessel had three cars, and placing a passenger in one of the
outer cars[13] distributed the load unevenly, so that the whole vessel
tilted over and crashed to the earth, the occupants luckily escaping
without injury. After Baumgarten’s death, Wolfert determined to carry
on with his experiments, and, having achieved a certain measure of
success, he announced an ascent to take place on the Tempelhofer
Field, near Berlin, on June 12th, 1897. The vessel, travelling with
the wind, reached a height of 600 feet, when the exhaust of the motor
communicated flame to the envelope of the balloon, and Wolfert,
together with a passenger he carried, was either killed by the fall or
burnt to death on the ground. Giffard had taken special precautions to
avoid an accident of this nature, and Wolfert, failing to observe equal
care, paid the full penalty.
Platz, a German soldier, attempting an ascent on the Tempelhofer Field
in the Schwartz airship in 1897, merely proved the dirigible a failure.
The vessel was of aluminium, 0.008 inch in thickness, strengthened by
an aluminium lattice work; the motor was two-cylindered petrol-driven;
at the first trial the metal developed such leaks that the vessel came
to the ground within four miles of its starting point. Platz, who was
aboard alone as crew, succeeded in escaping by jumping clear before
the car touched earth, but the shock of alighting broke up the balloon,
and a following high wind completed the work of full destruction. A
second account says that Platz, finding the propellers insufficient to
drive the vessel against the wind, opened the valve and descended too
rapidly.
The envelope of this dirigible was 156 feet in length, and the method
of filling was that of pushing in bags, fill them with gas, and
then pulling them to pieces and tearing them out of the body of the
balloon. A second contemplated method of filling was by placing a linen
envelope inside the aluminium casing, blowing it out with air, and then
admitting the gas between the linen and the aluminium outer casing.
This would compress the air out of the linen envelope, which was to be
withdrawn when the aluminium casing had been completely filled with gas.
All this, however, assumes that the Schwartz type--the first rigid
dirigible, by the way--would prove successful. As it proved a failure
on the first trial, the problem of filling it did not arise again.
By this time Zeppelin, retired from the German army, had begun to
devote himself to the study of dirigible construction, and, a year
after Schwartz had made his experiment and had failed, he got together
sufficient funds for the formation of a limited liability company, and
started on the construction of the first of his series of airships. The
age of tentative experiment was over, and, forerunner of the success
of the heavier-than-air type of flying machine, successful dirigible
flight was accomplished by Zeppelin in Germany, and by Santos-Dumont in
France.
III
SANTOS-DUMONT
A Brazilian by birth, Santos-Dumont began in Paris in the year 1898 to
make history, which he subsequently wrote. His book, _My Airships_,
is a record of his eight years of work on lighter-than-air machines,
a period in which he constructed no less than fourteen dirigible
balloons, beginning with a cubic capacity of 6,350 feet, and an engine
of 3 horse-power, and rising to a cubic capacity of 71,000 feet on the
tenth dirigible he constructed, and an engine of 60 horse-power, which
was fitted to the seventh machine in order of construction, the one
which he built after winning the Deutsch Prize.
The student of dirigible construction is recommended to Santos-Dumont’s
own book not only as a full record of his work, but also as one of
the best stories of aerial navigation that has ever been written.
Throughout all his experiments, he adhered to the non-rigid type; his
first dirigible made its first flight on September 18th, 1898, starting
from the Jardin d’Acclimatation to the west of Paris; he calculated
that his 3 horse-power engine would yield sufficient power to enable
him to steer clear of the trees with which the starting-point was
surrounded, but, yielding to the advice of professional aeronauts who
were present, with regard to the placing of the dirigible for his
start, he tore the envelope against the trees. Two days later, having
repaired the balloon, he made an ascent of 1,300 feet. In descending,
the hydrogen left in the balloon contracted, and Santos-Dumont narrowly
escaped a serious accident in coming to the ground.
His second machine, built in the early spring of 1899, held over 7,000
cubic feet of gas and gave a further 44 lbs. of ascensional force. The
balloon envelope was very long and very narrow; the first attempt at
flight was made in wind and rain, and the weather caused sufficient
contraction of the hydrogen for a wind gust to double the machine
up and toss it into the trees near its starting-point. The inventor
immediately set about the construction of ‘Santos-Dumont No. 3,’ on
which he made a number of successful flights, beginning on November
13th, 1899. On the last of his flights, he lost the rudder of the
machine and made a fortunate landing at Ivry. He did not repair the
balloon, considering it too clumsy in form and its motor too small.
Consequently No. 4 was constructed, being finished on the 1st August,
1900. It had a cubic capacity of 14,800 feet, a length of 129 feet and
greatest diameter of 16.7 feet, the power plant being a 7 horse-power
Buchet motor. Santos-Dumont sat on a bicycle saddle fixed to the long
bar suspended under the machine, which also supported motor, propeller,
ballast, and fuel. The experiment of placing the propeller at the stem
instead of at the stern was tried, and the motor gave it a speed of 100
revolutions per minute. Professor Langley witnessed the trials of the
machine, which proved before the members of the International Congress
of Aeronautics, on September 19th, that it was capable of holding its
own against a strong wind.
Finding that the cords with which his dirigible balloon cars were
suspended offered almost as much resistance to the air as did the
balloon itself, Santos-Dumont substituted piano wire and found that the
alteration constituted greater progress than many a more showy device.
He altered the shape and size of his No. 4 to a certain extent and
fitted a motor of 12 horse-power. Gravity was controlled by shifting
weights worked by a cord; rudder and propeller were both placed at the
stern. In Santos-Dumont’s book there is a certain amount of confusion
between the No. 4 and No. 5 airships, until he explains that ‘No.
5’ is the reconstructed ‘No. 4.’ It was with No. 5 that he won the
Encouragement Prize presented by the Scientific Commission of the Paris
Aero Club. This he devoted to the first aeronaut who between May and
October of 1900 should start from St Cloud, round the Eiffel Tower,
and return. If not won in that year, the prize was to remain open the
following year from May 1st to October 1st and so on annually until
won. This was a simplification of the conditions of the Deutsch Prize
itself, the winning of which involved a journey of 11 kilometres in 30
minutes.
The Santos-Dumont No. 5, which was in reality the modified No. 4 with
new keel, motor, and propeller, did the course of the Deutsch Prize,
but with it Santos-Dumont made no attempt to win the prize until July
of 1901, when he completed the course in 40 minutes, but tore his
balloon in landing. On the 8th August, with his balloon leaking, he
made a second attempt, and narrowly escaped disaster, the airship being
entirely wrecked. Thereupon he built No. 6 with a cubic capacity of
22,239 feet and a lifting power of 1,518 lbs. With this machine he won
the Deutsch Prize on October 19th, 1901, starting with the disadvantage
of a side wind of 20 feet per second. He reached the Eiffel Tower
in 9 minutes and, through miscalculating his turn, only just missed
colliding with it. He got No. 6 under control again and succeeded in
getting back to his starting-point in 29½ minutes, thus winning the
125,000 francs which constituted the Deutsch Prize, together with a
similar sum granted to him by the Brazilian Government for the exploit.
The greater part of this money was given by Santos-Dumont to charities.
He went on building after this until he had made fourteen non-rigid
dirigibles; of these No. 12 was placed at the disposal of the military
authorities, while the rest, except for one that was sold to an
American and made only one trip, were matters of experiment for their
maker. His conclusions from his experiments may be gathered from his
own work:--
‘On Friday, 31st July, 1903, Commandant Hirschauer and
Lieutenant-Colonel Bourdeaux spent the afternoon with me at my airship
station at Neuilly St James, where I had my three newest airships--the
racing ‘No. 7,’ the omnibus ‘No. 10,’ and the runabout ‘No. 9’--ready
for their study. Briefly, I may say that the opinions expressed by the
representatives of the Minister of War were so unreservedly favourable
that a practical test of a novel character was decided to be made.
Should the airship chosen pass successfully through it the result will
be conclusive of its military value.
‘Now that these particular experiments are leaving my exclusively
private control I will say no more of them than what has been already
published in the French press. The test will probably consist of an
attempt to enter one of the French frontier towns, such as Belfort or
Nancy, on the same day that the airship leaves Paris. It will not,
of course, be necessary to make the whole journey in the airship. A
military railway wagon may be assigned to carry it, with its balloon
uninflated, with tubes of hydrogen to fill it, and with all the
necessary machinery and instruments arranged beside it. At some station
a short distance from the town to be entered the wagon may be uncoupled
from the train, and a sufficient number of soldiers accompanying the
officers will unload the airship and its appliances, transport the
whole to the nearest open space, and at once begin inflating the
balloon. Within two hours from quitting the train the airship may be
ready for its flight to the interior of the technically-besieged town.
‘Such may be the outline of the task--a task presented imperiously to
French balloonists by the events of 1870–1, and which all the devotion
and science of the Tissandier brothers failed to accomplish. To-day
the problem may be set with better hope of success. All the essential
difficulties may be revived by the marking out of a hostile zone around
the town that must be entered; from beyond the outer edge of this zone,
then, the airship will rise and take its flight--across it.
‘Will the airship be able to rise out of rifle range? I have always
been the first to insist that the normal place of the airship is in
low altitudes, and I shall have written this book to little purpose
if I have not shown the reader the real dangers attending any brusque
vertical mounting to considerable heights. For this we have the
terrible Severo accident before our eyes. In particular, I have
expressed astonishment at hearing of experimenters rising to these
altitudes without adequate purpose in their early stages of experience
with dirigible balloons. All this is very different, however, from a
reasoned, cautious mounting, whose necessity has been foreseen and
prepared for.’
Probably owing to the fact that his engines were not of sufficient
power, Santos-Dumont cannot be said to have solved the problem of the
military airship, although the French Government bought one of his
vessels. At the same time, he accomplished much in furthering and
inciting experiment with dirigible airships, and he will always rank
high among the pioneers of aerostation. His experiments might have gone
further had not the Wright brothers’ success in America and French
interest in the problem of the heavier-than-air machine turned him
from the study of dirigibles to that of the aeroplane, in which also
he takes high rank among the pioneers, leaving the construction of a
successful military dirigible to such men as the Lebaudy brothers,
Major Parseval, and Zeppelin.
IV
THE MILITARY DIRIGIBLE
Although French and German experiment in connection with the production
of an airship which should be suitable for military purposes proceeded
side by side, it is necessary to outline the development in the two
countries separately, owing to the differing character of the work
carried out. So far as France is concerned, experiment began with the
Lebaudy brothers, originally sugar refiners, who turned their energies
to airship construction in 1899. Three years of work went to the
production of their first vessel, which was launched in 1902, having
been constructed by them together with a balloon manufacturer named
Surcouf and an engineer, Julliot. The Lebaudy airships were what is
known as semi-rigids, having a spar which ran practically the full
length of the gas bag to which it was attached in such a way as to
distribute the load evenly. The car was suspended from the spar, at
the rear end of which both horizontal and vertical rudders were fixed,
whilst stabilising fins were provided at the stern of the gas envelope
itself. The first of the Lebaudy vessels was named the ‘Jaune’; its
length was 183 feet and its maximum diameter 30 feet, while the cubic
capacity was 80,000 feet. The power unit was a 40 horse-power Daimler
motor, driving two propellers and giving a maximum speed of 26 miles
per hour. This vessel made 29 trips, the last of which took place in
November, 1902, when the airship was wrecked through collision with a
tree.
[Illustration: Astra Torres.]
The second airship of Lebaudy construction was 7 feet longer than the
first, and had a capacity of 94,000 cubic feet of gas with a triple air
bag of 17,500 cubic feet to compensate for loss of gas; this latter was
kept inflated by a rotary fan. The vessel was eventually taken over by
the French Government and may be counted the first dirigible airship
considered fit on its tests for military service.
Later vessels of the Lebaudy type were the ‘Patrie’ and ‘Republique,’
in which both size and method of construction surpassed those of the
two first attempts. The ‘Patrie’ was fitted with a 60 horse-power
engine which gave a speed of 28 miles an hour, while the vessel had a
radius of 280 miles, carrying a crew of nine. In the winter of 1907 the
‘Patrie’ was anchored at Verdun, and encountered a gale which broke her
hold on her mooring-ropes. She drifted derelict westward across France,
the Channel, and the British Isles, and was lost in the Atlantic.
The ‘Republique’ had an 80 horse-power motor, which, however, only gave
her the same speed as the ‘Patrie.’ She was launched in July, 1908,
and within three months came to an end which constituted a tragedy
for France. A propeller burst while the vessel was in the air, and
one blade, flying toward the envelope, tore in it a great gash; the
airship crashed to earth, and the two officers and two non-commissioned
officers who were in the car were instantaneously killed.
The Clement Bayard, and subsequently the Astra-Torres, non-rigids,
followed on the early Lebaudys and carried French dirigible
construction up to 1912. The Clement Bayard was a simple non-rigid
having four lobes at the stern end to assist stability. These were
found to retard the speed of the airship, which in the second and
more successful construction was driven by a Clement Bayard motor of
100 horse-power at a speed of 30 miles an hour. On August 23rd, 1909,
while being tried for acceptance by the military authorities, this
vessel achieved a record by flying at a height of 5,000 feet for two
hours. The Astra-Torres non-rigids were designed by a Spaniard, Señor
Torres, and built by the Astra Company. The envelope was of trefoil
shape, this being due to the interior rigging from the suspension band;
the exterior appearance is that of two lobes side by side, overlaid
by a third. The interior rigging, which was adopted with a view to
decreasing air resistance, supports a low-hung car from the centre of
the envelope; steering is accomplished by means of horizontal planes
fixed on the envelope at the stern, and vertical planes depending
beneath the envelope, also at the stern end.
One of the most successful of French pre-war dirigibles was a Clement
Bayard built in 1912. In this twin propellers were placed at the front
and horizontal and vertical rudders in a sort of box formation under
the envelope at the stern. The envelope was stream-lined, while the
car of the machine was placed well forward with horizontal controlling
planes above it and immediately behind the propellers. This airship,
which was named ‘Dupuy de Lome,’ may be ranked as about the most
successful non-rigid dirigible constructed prior to the War.
Experiments with non-rigids in Germany was mainly carried on by Major
Parseval, who produced his first vessel in 1906. The main feature
of this airship consisted in variation in length of the suspension
cables at the will of the operator, so that the envelope could be
given an upward tilt while the car remained horizontal in order to
give the vessel greater efficiency in climbing. In this machine, the
propeller was placed above and forward of the car, and the controlling
planes were fixed directly to the envelope near the forward end. A
second vessel differed from the first mainly in the matter of its
larger size, variable suspension being again employed, together with a
similar method of control. The vessel was moderately successful, and
under Major Parseval’s direction a third was constructed for passenger
carrying, with two engines of 120 horse-power, each driving propellers
of 13 feet diameter. This was the most successful of the early German
dirigibles; it made a number of voyages with a dozen passengers in
addition to its crew, as well as proving its value for military
purposes by use as a scout machine in manœuvres. Later Parsevals were
constructed of stream-line form, about 300 feet in length, and with
engines sufficiently powerful to give them speeds up to 50 miles an
hour.
Major Von Gross, commander of a Balloon Battalion, produced semi-rigid
dirigibles from 1907 onward. The second of these, driven by two 75
horse-power Daimler motors, was capable of a speed of 27 miles an
hour; in September of 1908 she made a trip from and back to Berlin
which lasted 13 hours, in which period she covered 176 miles with four
passengers and reached a height of 4,000 feet. Her successor, launched
in April of 1909, carried a wireless installation, and the next to
this, driven by four motors of 75 horse-power each, reached a speed of
45 miles an hour. As this vessel was constructed for military purposes,
very few details either of its speed or method of construction were
made public.
Practically all these vessels were discounted by the work of
Ferdinand von Zeppelin, who set out from the first with the idea of
constructing a rigid dirigible. Beginning in 1898, he built a balloon
on an aluminium framework covered with linen and silk, and divided
into interior compartments holding linen bags which were capable of
containing nearly 400,000 cubic feet of hydrogen. The total length of
this first Zeppelin airship was 420 feet and the diameter 38 feet.
Two cars were rigidly attached to the envelope, each carrying a 16
horse-power motor, driving propellers which were rigidly connected to
the aluminium framework of the balloon. Vertical and horizontal screws
were used for lifting and forward driving and a sliding weight was used
to raise or lower the stem of the vessel out of the horizontal in order
to rise or descend without altering the load by loss of ballast or the
lift by loss of gas.
The first trial of this vessel was made in July of 1900, and was
singularly unfortunate. The winch by which the sliding weight was
operated broke, and the balloon was so bent that the working of the
propellers was interfered with, as was the steering. A speed of 13 feet
per second was attained, but on descending the airship ran against some
piles and was further damaged. Repairs were completed by the end of
September, 1900, and on a second trial flight made on October 21st a
speed of 30 feet per second was reached.
[Illustration: Zeppelin, pre-war type.]
Zeppelin was far from satisfied with the performance of this vessel,
and he therefore set about collecting funds for the construction of
a second, which was completed in 1905. By this time the internal
combustion engine had been greatly improved, and without any increase
of weight, Zeppelin was able to instal two motors of 85 horse-power
each. The total capacity was 367,000 cubic feet of hydrogen, carried
in 16 gas bags inside the framework, and the weight of the whole
construction was 9 tons--a ton less than that of the first Zeppelin
airship. Three vertical planes at front and rear controlled horizontal
steering, while rise and fall was controlled by horizontal planes
arranged in box form. Accident attended the first trial of this second
airship, which took place over the Bodensee on November 30th, 1905. ‘It
had been intended to tow the raft, to which it was anchored, further
from the shore against the wind. But the water was too low to allow
the use of the raft. The balloon was therefore mounted on pontoons,
pulled out into the lake, and taken in tow by a motor-boat. It was
caught by a strong wind which was blowing from the shore, and driven
ahead at such a rate that it overtook the motor-boat. The tow rope was
therefore at once cut, but it unexpectedly formed into knots and became
entangled with the airship, pulling the front end down into the water.
The balloon was then caught by the wind and lifted into the air, when
the propellers were set in motion. The front end was at this instant
pointing in a downward direction, and consequently it shot into the
water, where it was found necessary to open the valves.’[14]
The damage done was repaired within six weeks, and the second trial
was made on January 17th, 1906. The lifting force was too great for
the weight, and the dirigible jumped immediately to 1,500 feet. The
propellers were started, and the dirigible brought to a lower level,
when it was found possible to drive against the wind. The steering
arrangements were found too sensitive, and the motors were stopped,
when the vessel was carried by the wind until it was over land--it had
been intended that the trial should be completed over water. A descent
was successfully accomplished and the dirigible was anchored for the
night, but a gale caused it so much damage that it had to be broken
up. It had achieved a speed of 30 feet per second with the motors
developing only 36 horse-power and, gathering from this what speed
might have been accomplished with the full 170 horse-power, Zeppelin
set about the construction of No. 3, with which a number of successful
voyages were made, proving the value of the type for military purposes.
No. 4 was the most notable of the early Zeppelins, as much on account
of its disastrous end as by reason of any superior merit in comparison
with No. 3. The main innovation consisted in attaching a triangular
keel to the under side of the envelope, with two gaps beneath which the
cars were suspended. Two Daimler Mercedes motors of 110 horse-power
each were placed one in each car, and the vessel carried sufficient
fuel for a 60-hour cruise with the motors running at full speed. Each
motor drove a pair of three-bladed metal propellers rigidly attached
to the framework of the envelope and about 15 feet in diameter. There
was a vertical rudder at the stern of the envelope and horizontal
controlling planes were fixed on the sides of the envelope. The best
performances and the end of this dirigible were summarised as follows
by Major Squier:--
‘Its best performances were two long trips performed during the
summer of 1908. The first, on July 4th, lasted exactly 12 hours,
during which time it covered a distance of 235 miles, crossing the
mountains to Lucerne and Zurich, and returning to the balloon-house
near Friedrichshafen, on Lake Constance. The average speed on this trip
was 32 miles per hour. On August 4th, this airship attempted a 24-hour
flight, which was one of the requirements made for its acceptance
by the Government. It left Friedrichshafen in the morning with the
intention of following the Rhine as far as Mainz, and then returning
to its starting-point, straight across the country. A stop of 3 hours
30 minutes was made in the afternoon of the first day on the Rhine, to
repair the engine. On the return, a second stop was found necessary
near Stuttgart, due to difficulties with the motors, and some loss of
gas. While anchored to the ground, a storm arose which broke loose
the anchorage, and, as the balloon rose in the air, it exploded and
took fire (due to causes which have never been actually determined and
published) and fell to the ground, where it was completely destroyed.
On this journey, which lasted in all 31 hours 15 minutes, the airship
was in the air 20 hours 45 minutes, and covered a total distance of 378
miles.
‘The patriotism of the German nation was aroused. Subscriptions
were immediately started, and in a short space of time a quarter of
a million pounds had been raised. A Zeppelin Society was formed to
direct the expenditure of this fund. Seventeen thousand pounds has
been expended in purchasing land near Friederichshafen; workshops were
erected, and it was announced that within one year the construction
of eight airships of the Zeppelin type would be completed. Since the
disaster to ‘Zeppelin IV.’ the Crown Prince of Germany made a trip in
‘Zeppelin No. 3,’ which had been called back into service, and within
a very few days the German Emperor visited Friedrichshafen for the
purpose of seeing the airship in flight. He decorated Count Zeppelin
with the Order of the Black Eagle. German patriotism and enthusiasm
has gone further, and the “German Association for an Aerial Fleet” has
been organised in sections throughout the country. It announces its
intention of building 50 garages (hangars) for housing airships.’
By January of 1909, with well over a quarter of a million in hand for
the construction of Zeppelin airships, No. 3 was again brought out,
probably in order to maintain public enthusiasm in respect of the
possible new engine of war. In March of that year No. 3 made a voyage
which lasted for 4 hours over and in the vicinity of Lake Constance; it
carried 26 passengers for a distance of nearly 150 miles.
Before the end of March, Count Zeppelin determined to voyage from
Friedrichshafen to Munich, together with the crew of the airship
and four military officers. Starting at four in the morning and
ascertaining their route from the lights of railway stations and the
ringing of bells in the towns passed over, the journey was completed
by nine o’clock, but a strong south-west gale prevented the intended
landing. The airship was driven before the wind until three o’clock
in the afternoon, when it landed safely near Dingolfing; by the next
morning the wind had fallen considerably and the airship returned to
Munich and landed on the parade ground as originally intended. At about
3.30 in the afternoon, the homeward journey was begun, Friedrichshafen
being reached at about 7.30.
These trials demonstrated that sufficient progress had been made to
justify the construction of Zeppelin airships for use with the German
army. No. 3 had been manœuvred safely if not successfully in half a
gale of wind, and henceforth it was known as ‘SMS. Zeppelin I.,’ at the
bidding of the German Emperor, while the construction of ‘SMS. Zeppelin
II.’ was rapidly proceeded with. The fifth construction of Count
Zeppelin’s was 446 feet in length, 42½ feet in diameter, and contained
530,000 cubic feet of hydrogen gas in 17 separate compartments. Trial
flights were made on the 26th May, 1909, and a week later she made a
record voyage of 940 miles, the route being from Lake Constance over
Ulm, Nuremberg, Leipzig, Bitterfeld, Weimar, Heilbronn, and Stuttgart,
descending near Goppingen; the time occupied in the flight was upwards
of 38 hours.
In landing, the airship collided with a pear-tree, which damaged the
bows and tore open two sections of the envelope, but repairs on the
spot enabled the return journey to Friedrichshafen to be begun 24
hours later. In spite of the mishap the Zeppelin had once more proved
itself as a possible engine of war, and thenceforth Germany pinned
its faith to the dirigible, only developing the aeroplane to such an
extent as to keep abreast of other nations. By the outbreak of war,
nearly 30 Zeppelins had been constructed; considerably more than
half of these were destroyed in various ways, but the experiments
carried on with each example of the type permitted of improvements
being made. The first fatality occurred in September, 1913, when the
fourteenth Zeppelin to be constructed, known as Naval Zeppelin L.1,
was wrecked in the North Sea by a sudden storm and her crew of thirteen
were drowned. About three weeks after this, Naval Zeppelin L.2, the
eighteenth in order of building, exploded in mid-air while manœuvring
over Johannisthal. She was carrying a crew of 25, who were all killed.
By 1912 the success of the Zeppelin type brought imitators. Chief among
them was the Schutte-Lanz, a Mannheim firm, which produced a rigid
dirigible with a wooden framework, wire braced. This was not a cylinder
like the Zeppelin, but reverted to the cigar shape and contained about
the same amount of gas as the Zeppelin type. The Schutte-Lanz was made
with two gondolas rigidly attached to the envelope in which the gas
bags were placed. The method of construction involved greater weight
than was the case with the Zeppelin, but the second of these vessels,
built with three gondolas containing engines, and a navigating cabin
built into the hull of the airship itself, proved quite successful as
a naval scout until wrecked on the islands off the coast of Denmark
late in 1914. The last Schutte-Lanz to be constructed was used by the
Germans for raiding England, and was eventually brought down in flames
at Cowley.
V
BRITISH AIRSHIP DESIGN
As was the case with the aeroplane, Great Britain left France and
Germany to make the running in the early days of airship construction;
the balloon section of the Royal Engineers was compelled to confine
its energies to work with balloons pure and simple until well after
the twentieth century had dawned, and such experiments as were made in
England were done by private initiative. As far back as 1900 Doctor
Barton built an airship at the Alexandra Palace and voyaged across
London in it. Four years later Mr E. T. Willows of Cardiff produced
the first successful British dirigible, a semi-rigid 74 feet in
length and 18 feet in diameter, engined with a 7 horse-power Peugot
twin-cylindered motor. This drove a two-bladed propeller at the stern
for propulsion, and also actuated a pair of auxiliary propellers at
the front which could be varied in their direction so as to control
the right and left movements of the airship. This device was patented
and the patent was taken over by the British Government, which by
1908 found Mr Willow’s work of sufficient interest to regard it as
furnishing data for experiment at the balloon factory at Farnborough.
In 1909, Willows steered one of his dirigibles to London from Cardiff
in a little less than ten hours, making an average speed of over 14
miles an hour. The best speed accomplished was probably considerably
greater than this, for at intervals of a few miles, Willows descended
near the earth to ascertain his whereabouts with the help of a
megaphone. It must be added that he carried a compass in addition to
his megaphone. He set out for Paris in November of 1910, reached the
French coast, and landed near Douai. Some damage was sustained in this
landing, but, after repair, the trip to Paris was completed.
Meanwhile the Government balloon factory at Farnborough began airship
construction in 1907; Colonel Capper, R.E., and S. F. Cody were jointly
concerned in the production of a semi-rigid. Fifteen thicknesses of
goldbeaters’ skin--about the most expensive covering obtainable--were
used for the envelope, which was 25 feet in diameter. A slight shower
of rain in which the airship was caught led to its wreckage, owing to
the absorbent quality of the goldbeaters’ skin, whereupon Capper and
Cody set to work to reproduce the airship and its defects on a larger
scale. The first had been named ‘Nulli Secundus’ and the second was
named ‘Nulli Secundus II.’ _Punch_ very appropriately suggested that
the first vessel ought to have been named ‘Nulli Primus,’ while a
possible third should be christened ‘Nulli Tertius.’ ‘Nulli Secundus
II.’ was fitted with a 100 horse-power engine and had an envelope of 42
feet in diameter, the goldbeaters’ skin being covered in fabric and the
car being suspended by four bands which encircled the balloon envelope.
In October of 1907, ‘Nulli Secundus II.’ made a trial flight from
Farnborough to London and was anchored at the Crystal Palace. The wind
sprung up and took the vessel away from its mooring ropes, wrecking
it after the one flight.
[Illustration: The Army Airship ‘Beta’ at the Manœuvres.
The ‘Beta’ going up to reconnoitre.]
Stagnation followed until early in 1909, when a small airship fitted
with two 12 horse-power motors and named the ‘Baby’ was turned out from
the balloon factory. This was almost egg-shaped, the blunt end being
forward, and three inflated fins being placed at the tail as control
members. A long car with rudder and elevator at its rear-end carried
the engines and crew; the ‘Baby’ made some fairly successful flights
and gave a good deal of useful data for the construction of later
vessels.
Next to this was ‘Army Airship 2A’ launched early in 1910 and larger,
longer, and narrower in design than the Baby. The engine was an 80
horse-power Green motor which drove two pairs of propellers; small
inflated control members were fitted at the stern end of the envelope,
which was 154 feet in length. The suspended car was 84 feet long,
carrying both engines and crew, and the Willows idea of swivelling
propellers for governing the direction was used in this vessel. In June
of that year a new, small-type dirigible, the ‘Beta,’ was produced,
driven by a 30 horse-power Green engine with which she flew over 3,000
miles. She was the most successful British dirigible constructed up
to that time, and her successor, the ‘Gamma,’ was built on similar
lines. The ‘Gamma’ was a larger vessel, however, produced in 1912, with
flat, controlling fins and rudder at the rear end of the envelope,
and with the conventional long car suspended at some distance beneath
the gas bag. By this time, the mooring mast, carrying a cap of which
the concave side fitted over the convex nose of the airship, had been
originated. The cap was swivelled, and, when attached to it, an
airship was held nose on to the wind, thus reducing by more than half
the dangers attendant on mooring dirigibles in the open.
Private subscription under the auspices of the _Morning Post_ got
together sufficient funds in 1910 for the purchase of a Lebaudy
airship, which was built in France, flown across the Channel, and
presented to the Army Airship Fleet. This dirigible was 337 feet long,
and was driven by two 135 horse-power Panhard motors, each of which
actuated two propellers. The journey from Moisson to Aldershot was
completed at a speed of 36 miles an hour, but the airship was damaged
while being towed into its shed. On May of the following year, the
Lebaudy was brought out for a flight, but, in landing, the guide rope
fouled in trees and sheds and brought the airship broadside on to the
wind; she was driven into some trees and wrecked to such an extent that
rebuilding was considered an impossibility. A Clement Bayard, bought by
the army airship section, became scrap after even less flying than had
been accomplished by the Lebaudy.
In April of 1910, the Admiralty determined on a naval air service, and
set about the production of rigid airships which should be able to
compete with Zeppelins as naval scouts. The construction was entrusted
to Vickers, Ltd., who set about the task at their Barrow works and
built something which, when tested after a year’s work, was found
incapable of lifting its own weight. This defect was remedied by a
series of alterations, and meanwhile the unofficial title of ‘Mayfly’
was given to the vessel.
[Illustration: The S.S. type of airship.
H.M. King George inspecting.]
Taken over by the Admiralty before she had passed any flying tests,
the ‘Mayfly’ was brought out on September 24th, 1911, for a trial trip,
being towed out from her shed by a tug. When half out from the shed,
the envelope was caught by a light cross-wind, and, in spite of the
pull from the tug, the great fabric broke in half, nearly drowning the
crew, who had to dive in order to get clear of the wreckage.
There was considerable similarity in form, though not in performance,
between the Mayfly and the pre-war Zeppelin. The former was 510 feet in
length, cylindrical in form, with a diameter of 48 feet, and divided
into 19 gas-bag compartments. The motive power consisted of two 200
horse-power Wolseley engines. After its failure, the Naval Air Service
bought an Astra-Torres airship from France and a Parseval from Germany,
both of which proved very useful in the early days of the War, doing
patrol work over the Channel before the Blimps came into being.
Early in 1915 the ‘Blimp’ or ‘S.S.’ type of coastal airship was evolved
in response to the demand for a vessel which could be turned out
quickly and in quantities. There was urgent demand, voiced by Lord
Fisher, for a type of vessel capable of maintaining anti-submarine
patrol off the British coasts, and the first S.S. airships were made by
combining a gasbag with the most available type of aeroplane fuselage
and engine, and fitting steering gear. The ‘Blimp’ consisted of a B.E.
fuselage with engine and geared-down propeller, and seating for pilot
and observer, attached to an envelope about 150 feet in length. With a
speed of between 35 and 40 miles an hour, the ‘Blimp’ had a cruising
capacity of about ten hours; it was fitted with wireless set, camera,
machine-gun, and bombs, and for submarine spotting and patrol work
generally it proved invaluable, though owing to low engine power and
comparatively small size, its uses were restricted to reasonably fair
weather. For work farther out at sea and in all weathers, airships
known as the coast patrol type, and more commonly as ‘coastals,’
were built, and later the ‘N.S.’ or North Sea type, still larger and
more weather-worthy, followed. By the time the last year of the War
came, Britain led the world in the design of non-rigid and semi-rigid
dirigibles. The ‘S.S.’ or ‘Blimp’ had been improved to a speed of 50
miles an hour, carrying a crew of three, and the endurance record for
the type was 18½ hours, while one of them had reached a height of
10,000 feet. The North Sea type of non-rigid was capable of travelling
over 20 hours at full speed, or forty hours at cruising speed, and the
number of non-rigids belonging to the British Navy exceeded that of any
other country.
It was owing to the incapacity--apparent or real--of the British
military or naval designers to produce a satisfactory rigid airship
that the ‘N.S.’ airship was evolved. The first of this type was
produced in 1916, and on her trials she was voted an unqualified
success, in consequence of which the building of several more was
pushed on. The envelope, of 360,000 cubic feet capacity, was made on
the Astra-Torres principle of three lobes, giving a trefoil section.
The ship carried four fins, to three of which the elevator and rudder
flaps were attached; petrol tanks were placed inside the envelope,
under which was rigged a long covered-in car, built up of a light
steel tubular framework 35 feet in length. The forward portion was
covered with duralumin sheeting, an aluminium alloy which, unlike
aluminium itself, is not affected by the action of sea air and water,
and the remainder with fabric laced to the framework. Windows and
port-holes were provided to give light to the crew, and the controls
and navigating instruments were placed forward, with the sleeping
accommodation aft. The engines were mounted in a power unit structure,
separate from the car and connected by wooden gangways supported by
wire cables. A complete electrical installation of two dynamos and
batteries for lights, signalling lamps, wireless, telephones, etc., was
carried, and the motive power consisted of either two 250 horse-power
Rolls-Royce engines or two 240 horse-power Fiat engines. The principal
dimensions of this type are length 262 feet, horizontal diameter 56
feet 9 inches, vertical diameter 69 feet 3 inches. The gross lift is
24,300 lbs. and the disposable lift without crew, petrol, oil, and
ballast 8,500 lbs. The normal crew carried for patrol work was ten
officers and men. This type holds the record of 101 hours continuous
flight on patrol duty.
In the matter of rigid design it was not until 1913 that the British
Admiralty got over the fact that the ‘Mayfly’ would not, and decided
on a further attempt at the construction of a rigid dirigible. The
contract for this was signed in March of 1914; work was suspended in
the following February and begun again in July, 1915, but it was not
until January of 1917 that the ship was finished, while her trials
were not completed until March of 1917, when she was taken over by
the Admiralty. The details of the construction and trial of this
vessel, known as ‘No. 9,’ go to show that she did not quite fill the
contract requirements in respect of disposable lift until a number
of alterations had been made. The contract specified that a speed of
at least 45 miles per hour was to be attained at full engine power,
while a minimum disposable lift of 5 tons was to be available for
movable weights, and the airship was to be capable of rising to a
height of 2,000 feet. Driven by four Wolseley Maybach engines of 180
horse-power each, the lift of the vessel was not sufficient, so it was
decided to remove the two engines in the after car and replace them by
a single engine of 250 horse-power. With this the vessel reached the
contract speed of 45 miles per hour with a cruising radius of 18 hours,
equivalent to 800 miles when the engines were running at full speed.
The vessel served admirably as a training airship, for, by the time she
was completed, the No. 23 class of rigid airship had come to being, and
thus No. 9 was already out of date.
Three of the 23 class were completed by the end of 1917; it was
stipulated that they should be built with a speed of at least 55
miles per hour, a minimum disposable lift of 8 tons, and a capability
of rising at an average rate of not less than 1,000 feet per minute
to a height of 3,000 feet. The motive power consisted of four 250
horse-power Rolls-Royce engines, one in each of the forward and
after cars and two in a centre car. Four-bladed propellers were used
throughout the ship.
[Illustration: Coastal airship, showing gun on top of envelope.]
A 23X type followed on the 23 class, but by the time two ships had been
completed, this was practically obsolete. The No. 31 class followed the
23X; it was built on Schutte-Lanz lines, 615 feet in length, 66 feet
diameter, and a million and a half cubic feet capacity. The hull was
similar to the later types of Zeppelin in shape, with a tapering stern
and a bluff, rounded bow. Five cars each carrying a 250 horse-power
Rolls-Royce engine, driving a single fixed propeller, were fitted,
and on her trials R.31 performed well, especially in the matter of
speed. But the experiment of constructing in wood in the Schutte-Lanz
way adopted with this vessel resulted in failure eventually, and the
type was abandoned.
Meanwhile, Germany had been pushing forward Zeppelin design and
straining every nerve in the improvement of rigid dirigible
construction, until L.33 was evolved; she was generally known as a
super-Zeppelin, and on September 24th, 1916, six weeks after her
launching, she was damaged by gun-fire in a raid over London, being
eventually compelled to come to earth at Little Wigborough in Essex.
The crew gave themselves up after having set fire to the ship, and
though the fabric was totally destroyed, the structure of the hull
remained intact, so that just as Germany was able to evolve the
Gotha bomber from the Handley-Page delivered at Lille, British naval
constructors were able to evolve the R.33 type of airship from the
Zeppelin framework delivered at Little Wigborough. Two vessels, R.33
and R.34, were laid down for completion; three others were also put
down for construction, but, while R.33 and R.34 were built almost
entirely from the data gathered from the wrecked L.33, the three later
vessels embody more modern design, including a number of improvements,
and more especially greater disposable lift. It has been commented
that while the British authorities were building R.33 and R.34,
Germany constructed 30 Zeppelins on 4 slips, for which reason it may
be reckoned a matter for congratulation that the rigid airship did not
decide the fate of the War. The following particulars of construction
of the R.33 and R.34 types are as given by Major Whale in his survey of
_British Airships_:--
‘In all its main features the hull structure of R.33 and R.34 follows
the design of the wrecked German Zeppelin airship L.33. The hull
follows more nearly a true stream-line shape than in the previous ships
constructed of duralumin, in which a greater proportion of the greater
length was parallel-sided. The Germans adopted this new shape from the
Schutte-Lanz design and have not departed from this practice. This
consists of a short, parallel body with a long, rounded bow and a long
tapering stem culminating in a point. The overall length of the ship is
643 feet with a diameter of 79 feet and an extreme height of 92 feet.
The type of girders in this class has been much altered from those in
previous ships. The hull is fitted with an internal triangular keel
throughout practically the entire length. This forms the main corridor
of the ship, and is fitted with a footway down the centre for its
entire length. It contains water ballast and petrol tanks, bomb storage
and crew accommodation, and the various control wires, petrol pipes,
and electric leads are carried along the lower part.
Throughout this internal corridor runs a bridge girder, from which
the petrol and water ballast tanks are supported. These tanks are so
arranged that they can be dropped clear of the ship. Amidships is the
cabin space with sufficient room for a crew of twenty-five. Hammocks
can be swung from the bridge girder before mentioned.
In accordance with the latest Zeppelin practice, monoplane rudders and
elevators are fitted to the horizontal and vertical fins.
The ship is supported in the air by nineteen gas bags, which give a
total capacity of approximately two million cubic feet of gas. The
gross lift works out at approximately 59½ tons, of which the total
fixed weight is 33 tons, giving a disposable lift of 26½ tons.
The arrangement of cars is as follows: At the forward end the control
car is slung, which contains all navigating instruments and the various
controls. Adjoining this is the wireless cabin, which is also fitted
for wireless telephony. Immediately aft of this is the forward power
car containing one engine, which gives the appearance that the whole is
one large car.
Amidships are two wing cars, each containing a single engine. These
are small and just accommodate the engines with sufficient room for
mechanics to attend to them. Further aft is another larger car which
contains an auxiliary control position and two engines.
It will thus be seen that five engines are installed in the ship; these
are all of the same type and horse-power, namely, 250 horse-power
Sunbeam. R.33 was constructed by Messrs Armstrong, Whitworth, Ltd.;
while her sister ship R.34 was built by Messrs Beardmore on the Clyde.’
Of the two vessels, R.34 appeared rather more airworthy than her sister
ship; the lift of the ship justified the carrying of a greater quantity
of fuel than had been provided for, and, as she was considered suitable
for making a Transatlantic crossing, extra petrol tanks were fitted
in the hull and a new type of outer cover was fitted with a view to
her making the Atlantic crossing. She made a 21 hour cruise over the
North of England and the South of Scotland at the end of May, 1919,
and subsequently went for a longer cruise over Denmark, the Baltic, and
the north coast of Germany, remaining in the air for 56 hours in spite
of very bad weather conditions. Finally, July 2nd was selected as the
starting date for the cross Atlantic flight; the vessel was commanded
by Major G. H. Scott, A.F.C., with Captain G. S. Greenland as first
officer, Second-Lieut. H. F. Luck as second officer, and Lieut. J. D.
Shotter as engineer officer. There were also on board Brig.-Gen. E. P.
Maitland, representing the Air Ministry, Major J. E. M. Pritchard,
representing the Admiralty, and Lieut.-Col. W. H. Hemsley of the Army
Aviation Department. In addition to eight tons of petrol, R.34 carried
a total number of 30 persons from East Fortune to Long Island, N.Y.
There being no shed in America capable of accommodating the airship,
she had to be moored in the open for refilling with fuel and gas, and
to make the return journey almost immediately.
[Illustration: The R 34 landing at Pulham St Mary on arrival from
America.]
Brig.-Gen. Maitland’s account of the flight, in itself a record as
interesting as valuable, divides the outward journey into two main
stages, the first from East Fortune to Trinity Bay, Newfoundland, a
distance of 2,050 sea miles, and the second and more difficult stage
to Mineola Field, Long Island, 1,080 sea miles. An easy journey was
experienced until Newfoundland was reached, but then storms and
electrical disturbances rendered it necessary to alter the course, in
consequence of which petrol began to run short. Head winds rendered the
shortage still more acute, and on Saturday, July 5th, a wireless signal
was sent out asking for destroyers to stand by to tow. However, after
an anxious night, R.34 landed safely at Mineola Field at 9.55 a.m.
on July 6th, having accomplished the journey in 108 hours 12 minutes.
She remained at Mineola until midnight of July 9th, when, although
it had been intended that a start should be made by daylight for
the benefit of New York spectators, an approaching storm caused
preparations to be advanced for immediate departure. She set out at
5.57 a.m. by British summer time, and flew over New York in the full
glare of hundreds of searchlights before heading out over the Atlantic.
A following wind assisted the return voyage, and on July 13th, at 7.57
a.m., R.34 anchored at Pulham, Norfolk, having made the return journey
in 75 hours 3 minutes, and proved the suitability of the dirigible
for Transatlantic commercial work. R.80, launched on July 19th, 1920,
afforded further proof, if this were needed.
It is to be noted that nearly all the disasters to airships have
been caused by launching and landing--the type is safe enough in
the air, under its own power, but its bulk renders it unwieldy for
ground handling. The German system of handling Zeppelins in and out
of their sheds is, so far, the best devised: this consists of heavy
trucks running on rails through the sheds and out at either end;
on descending, the trucks are run out, and the airship is securely
attached to them outside the shed; the trucks are then run back into
the shed, taking the airship with them, and preventing any possibility
of the wind driving the envelope against the side of the shed before it
is safely housed; the reverse process is adopted in launching, which is
thus rendered as simple as it is safe.
VI
THE AIRSHIP COMMERCIALLY
Prior to the war period, between the years 1910 and 1914, a German
undertaking called the Deutsche Luftfahrt Actien Gesellschaft conducted
a commercial Zeppelin service in which four airships known as the
Sachsan, Hansa, Victoria Louise, and Schwaben were used. During the
four years of its work, the company carried over 17,000 passengers,
and over 100,000 miles were flown without incurring one fatality and
with only minor and unavoidable accidents to the vessels composing
the service. Although a number of English notabilities made voyages
in these airships, the success of this only experiment in commercial
aerostation seems to have been forgotten since the war. There was
beyond doubt a military aim in this apparently peaceful use of Zeppelin
airships; it is past question now that all Germany’s mechanical
development in respect of land, sea, and air transport in the years
immediately preceding the war, was accomplished with the ulterior
aim of military conquest, but, at the same time, the running of this
service afforded proof of the possibility of establishing a dirigible
service for peaceful ends, and afforded proof too, of the value of the
dirigible as a vessel of purely commercial utility.
[Illustration: The ‘Bodensee’ German passenger balloon.]
In considering the possibility of a commercial dirigible service, it
is necessary always to bear in mind the disadvantages of first cost
and upkeep as compared with the aeroplane. The building of a modern
rigid is an exceedingly costly undertaking, and the provision of an
efficient supply of hydrogen gas to keep its compartments filled is a
very large item in upkeep of which the heavier-than-air machine goes
free. Yet the future of commercial aeronautics so far would seem to lie
with the dirigible where very long voyages are in question. No matter
how the aeroplane may be improved, the possibility of engine failure
always remains as a danger for work over water. In seaplane or flying
boat form, the danger is still present in a rough sea, though in the
American Transatlantic flight, N.C.3, taxi-ing 300 miles to the Azores
after having fallen to the water, proved that this danger is not so
acute as is generally assumed. Yet the multiple-engined rigid, as R.34
showed on her return voyage, may have part of her power plant put out
of action altogether and still complete her voyage very successfully,
which, in the case of mail carrying and services run strictly to time,
gives her an enormous advantage over the heavier-than-air machine.
‘For commercial purposes,’ General Sykes has remarked, ‘the airship
is eminently adapted for long distance journeys involving non-stop
flights. It has this inherent advantage over the aeroplane, that while
there appears to be a limit to the range of the aeroplane as at present
constructed, there is practically no limit whatever to that of the
airship, as this can be overcome by merely increasing the size. It thus
appears that for such journeys as crossing the Atlantic, or crossing
the Pacific from the west coast of America to Australia or Japan, the
airship will be peculiarly suitable. It having been conceded that the
scope of the airship is long distance travel, the only type which need
be considered for this purpose is the rigid. The rigid airship is still
in an embryonic state, but sufficient has already been accomplished
in this country, and more particularly in Germany, to show that with
increased capacity there is no reason why, within a few years’ time,
airships should not be built capable of completing the circuit of the
globe and of conveying sufficient passengers and merchandise to render
such an undertaking a paying proposition.’
The British R.38 class, embodying the latest improvements in airship
design outside Germany, gives a gross lift per airship of 85 tons and
a net lift of about 45 tons. The capacity of the gas bags is about two
and three-quarter million cubic feet, and, travelling at the rate of 45
miles per hour, the cruising range of the vessel is estimated at 8·8
days. Six engines, each of 350 horse-power, admit of an extreme speed
of 70 miles per hour if necessary.
The last word in German design is exemplified in the rigids L.70 and
L.71, together with the commercial airship ‘Bodensee.’ Previous to
the construction of these, the L.65 type is noteworthy as being the
first Zeppelin in which direct drive of the propeller was introduced,
together with an improved and lighter type of car. L.70, built in 1918
and destroyed by the British naval forces, had a speed of about 75
miles per hour; L.71 had a maximum speed of 72 miles per hour, a gas
bag capacity of 2,420,000 cubic feet, and a length of 743 feet, while
the total lift was 73 tons. Progress in design is best shown by the
progress in useful load; in the L.70 and L.71 class, this has been
increased to 58·3 per cent, while in the Bodensee it was even higher.
As was shown in R.34’s American flight, the main problem in connection
with the commercial use of dirigibles is that of mooring in the open.
The nearest to a solution of this problem, so far, consists in the
mast carrying a swivelling cap; this has been tried in the British
service with a non-rigid airship, which was attached to a mast in open
country in a gale of 52 miles an hour without the slightest damage to
the airship. In its commercial form, the mast would probably take the
form of a tower, at the top of which the cap would revolve so that
the airship should always face the wind, the tower being used for
embarkation and disembarkation of passengers and the provision of fuel
and gas. Such a system would render sheds unnecessary except in case of
repairs, and would enormously decrease the establishment charges of any
commercial airship.
All this, however, is hypothetical. Remains the airship of to-day,
developed far beyond the promise of five years ago, capable, as has
been proved by its achievements both in Britain and in Germany, of
undertaking practically any given voyage with success.
VII
KITE BALLOONS
As far back as the period of the Napoleonic wars, the balloon was given
a place in warfare, but up to the Franco-Prussian War of 1870–71 its
use was intermittent. The Federal forces made use of balloons to a
small extent in the American Civil War; they came to great prominence
in the siege of Paris, carrying out upwards of three million letters
and sundry carrier pigeons which took back messages into the besieged
city. Meanwhile, as captive balloons, the German and other armies
used them for observation and the direction of artillery fire. In
this work the ordinary spherical balloon was at a grave disadvantage;
if a gust of wind struck it, the balloon was blown downward and down
wind, generally twirling in the air and upsetting any calculations
and estimates that might be made by the observers, while in a wind
of 25 miles an hour it could not rise at all. The rotatory movement
caused by wind was stopped by an experimenter in the Russo-Japanese
war, who fixed to the captive observation balloons a fin which acted
as a rudder. This did not stop the balloon from being blown downward
and away from its mooring station, but this tendency was overcome by a
modification designed in Germany by the Parseval-Siegsfield Company,
which originated what has since become familiar as the ‘Sausage’
or kite balloon. This is so arranged that the forward end is
tilted up into the wind, and the underside of the gas bag, acting
as a plane, gives the balloon a lifting tendency in a wind, thus
counteracting the tendency of the wind to blow it downward and away
from its mooring station. Smaller bags are fitted at the lower and rear
end of the balloon with openings that face into the wind; these are
thus kept inflated, and they serve the purpose of a rudder, keeping the
kite balloon steady in the air.
[Illustration: An early type of the Parseval-Siegsfeld observation
balloon.
Used by the Germans in Russia.]
[Illustration: An observation balloon about to ascend to watch enemy
movements, near Metz, 25th January, 1918.]
Various types of kite balloon have been introduced; the original German
Parseval-Siegsfield had a single air bag at the stern end, which was
modified to two, three, or more lobes in later varieties, while an
American experimental design attempted to do away with the attached
lobes altogether by stringing out a series of small air bags, kite
fashion, in rear of the main envelope. At the beginning of the War,
Germany alone had kite balloons, for the authorities of the Allied
armies considered that the bulk of such a vessel rendered it too
conspicuous a mark to permit of its being serviceable. The Belgian
arm alone possessed two which, on being put into service, were found
extremely useful. The French followed by constructing kite balloons at
Chalais Meudon, and then, after some months of hostilities and with the
example of the Royal Naval Air Service to encourage them, the British
military authorities finally took up the construction and use of kite
balloons for artillery-spotting and general observation purposes.
Although many were brought down by gun-fire, their uses far outweighed
their disadvantages, and toward the end of the War, hardly a mile of
front was without its ‘Sausage.’
For naval work, kite balloons were carried in a specially constructed
hold in the forepart of certain vessels; when required for use, the
covering of the hold was removed, the kite balloon inflated and
released to the required height by means of winches as in the case
of the land work. The perfecting of the ‘Coastal’ and N.S. types of
airship, together with the extension of wireless telephony between
airship and cruiser or other warship, in all probability will render
the use of the kite balloon unnecessary in connection with naval
scouting. But, during the War, neither wireless telephony nor naval
airships had developed sufficiently to render the Navy independent of
any means that might come to hand, and the fitting of kite balloons in
this fashion filled a need of the times.
A necessary accessory of the kite balloon is the parachute, which has a
long history. Da Vinci and Veranzio (_ante_, page 119) appear to have
been the first exponents, the first in the theory and the latter in the
practice of parachuting. Mongolfier experimented at Annonay before he
constructed his first hot air-balloon, and in 1783 a certain Lenormand
dropped from a tree in a parachute. Blanchard the balloonist made a
spectacle of parachuting, and made it a financial success; Cocking,
in 1836, attempted to use an inverted form of parachute; taken up to
a height of 3,000 feet, he was cut adrift, when the framework of the
parachute collapsed and Cocking was killed.
[Illustration: In mid-air. A parachute descent from one of our balloons
at the front, near Metz, 26th January, 1918.]
The rate of fall is slow in parachuting to the ground. Frau Poitevin,
making a descent from a height of 6,000 feet, took 45 minutes to reach
the ground, and, when she alighted, her husband, who had taken her up,
had nearly got his balloon packed up. Robertson, another parachutist,
is said to have descended from a height of 10,000 feet in 35
minutes, or at a rate of nearly 5 feet per second. During the War
Brigadier-General Maitland made a parachute descent from a height of
10,000 feet, the time taken being about 20 minutes.
The parachute was developed considerably during the War period, the
main requirement, that of certainty in opening, being considerably
developed. Considered a necessary accessory for kite balloons, the
parachute was also partially adopted for use with aeroplanes in the
later War period, when it was contended that if a machine were shot
down in flames, its occupants would be given a far better chance of
escape if they had parachutes. Various trials were made to demonstrate
the extreme efficiency of the parachute in modern form, one of them
being a descent from the upper ways of the Tower Bridge to the waters
of the Thames, in which short distance the ‘Guardian Angel’ type of
parachute opened and cushioned the descent for its user.
For dirigibles, balloons, and kite balloons the parachute is an
essential. It would seem to be equally essential in the case of
heavier-than-air machines, but this point is still debated. Certainly
it affords the occupant of a falling aeroplane a chance, no matter how
slender, of reaching the ground in safety, and, for that reason, it
would seem to have a place in aviation as well as in aerostation.