A History of Aeronautics Part 16

[*] Hildebrandt.

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 This would compress the air out of the linen envelope, which was to be withdrawn when the aluminium casing had been completely filled with gas.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, a.s.sumes 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 limitedliability 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 subst.i.tuted piano wire and found that the alteration const.i.tuted 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 29 1/2 minutes, thus winning the 125,000 francs which const.i.tuted 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 pa.s.s 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 a.s.signed 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 s.p.a.ce, 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 alt.i.tudes, 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 alt.i.tudes 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 Pa.r.s.eval, 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.

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 surpa.s.sed 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 anch.o.r.ed 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 const.i.tuted 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 a.s.sist stability. These were found to r.e.t.a.r.d 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, Senor 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 Pa.r.s.eval, 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 Pa.r.s.eval's direction a third was constructed for pa.s.senger carrying, with two engines of 120 horsepower, 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 pa.s.sengers in addition to its crew, as well as proving its value for military purposes by use as a scout machine in manoeuvres. Later Pa.r.s.evals 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 pa.s.sengers 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.

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 anch.o.r.ed, further from the sh.o.r.e 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 sh.o.r.e, 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.'[*]

[*] Hildebrandt, Airships Past and Present.

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 anch.o.r.ed 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 anch.o.r.ed 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 s.p.a.ce 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 Friedrichshafen; 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 a.s.sociation 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 pa.s.sengers 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 pa.s.sed 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 manoeuvred 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, 42 1/2 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 manoeuvring 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.