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 lateral7 motion in rising and falling, and deduced that by alternate lowering and raising of such surfaces he would be able to navigate8 the air, regulating ascent9 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 150332 feet in length, with a vertical10 surface in front and a horizontal surface behind, might be navigated11 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 axis12 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, entrusted13 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 propulsive14 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 exasperated15 at successive delays, and in the end, thinking that the balloon would never rise, they destroyed it.
333 Meusnier, a French general, first conceived the idea of compensating16 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 steered17 by a rudder. A violent swirl18 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 ascended20, and at 16,000 feet he thrust a staff through the envelope—another account says that he slit21 it with his sword—and thus prevented disaster. The descent after this rip in the fabric22 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 entirely23 rigid24 connection between the car and the body of the balloon, as indispensable to a dirigible.12 He suggested using three propellers25, which were to be driven by hand by means of pulleys, and calculated that a crew of eighty would be required to furnish sufficient motive27 power. Horizontal fins28 were to be used to assure stability, and Meusnier thoroughly334 investigated the pressures exerted by gases, in order to ascertain30 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, acting31 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 ascents32 when he turned to aeronautical33 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 enthusiasts34, diverging35 from335 Meusnier’s ideas by making the ends pointed36, 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 triangular37 sail was placed vertically38 to act as rudder. The car, slung39 20 feet below the spar, carried the engine and propeller26. Engine and boiler40 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 attained41 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 specially43 covered to ensure a stiffening44 effect. The car of this dirigible was dropped rather lower than that of the first machine, in order to provide more thoroughly29 against the danger of explosions. Giffard, with a companion named Yon as passenger, took a trial trip on this vessel45, and made a journey against the wind, though slowly. In commencing to descend46, the nose of the envelope tilted47 upwards48, and the weight336 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 attain42 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 boilers49, 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 vessels50 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 revolved51 by the efforts of eight men. The vessel attained to337 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 forerunner52 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 cylinders53, 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 fully54 inflated55 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 combustion56 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 ascend19. 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 previously57.
Two brothers, Albert and Gaston Tissandier, were338 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 varnished58 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 1? 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 torpedo59 shape, 165 feet in length, and of just over 27 feet greatest diameter—the greatest diameter was at the front, and the cubic339 capacity was 66,000 feet. The car itself was 108 feet in length, and 4? 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 counteracted60 by rendering61 it possible to raise the axis on which the blades were mounted, and a guide rope was used to obviate62 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 determined63 that the air speed of the dirigible was no less than 14? 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 the340 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 cars13 distributed the load unevenly64, 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 aluminium65, 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 aboard341 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 insufficient66 to drive the vessel against the wind, opened the valve and descended67 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 contemplated68 method of filling was by placing a linen69 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 withdrawn70 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, retired71 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.
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1
navigating
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| v.给（船舶、飞机等）引航，导航( navigate的现在分词 )；（从海上、空中等）横越；横渡；飞跃 | |
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oars
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| n.桨，橹( oar的名词复数 )；划手v.划（行）( oar的第三人称单数 ) | |
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retard
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| n.阻止，延迟；vt.妨碍，延迟，使减速 | |
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deviation
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| n.背离，偏离；偏差，偏向；离题 | |
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divergences
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| n.分叉( divergence的名词复数 )；分歧；背离；离题 | |
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accomplished
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| adj.有才艺的；有造诣的；达到了的 | |
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lateral
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| adj.侧面的，旁边的 | |
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navigate
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| v.航行，飞行；导航，领航 | |
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ascent
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| n.(声望或地位)提高；上升，升高；登高 | |
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vertical
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| adj.垂直的，顶点的，纵向的；n.垂直物，垂直的位置 | |
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11
navigated
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| v.给（船舶、飞机等）引航，导航( navigate的过去式和过去分词 )；（从海上、空中等）横越；横渡；飞跃 | |
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axis
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| n.轴，轴线，中心线；坐标轴，基准线 | |
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entrusted
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| v.委托，托付( entrust的过去式和过去分词 ) | |
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propulsive
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| adj.推进的 | |
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exasperated
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| adj.恼怒的 | |
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compensating
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| 补偿，补助，修正 | |
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steered
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| v.驾驶( steer的过去式和过去分词 )；操纵；控制；引导 | |
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swirl
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| v.(使)打漩，(使)涡卷；n.漩涡，螺旋形 | |
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ascend
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| vi.渐渐上升，升高；vt.攀登，登上 | |
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ascended
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| v.上升，攀登( ascend的过去式和过去分词 ) | |
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slit
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| n.狭长的切口；裂缝；vt.切开，撕裂 | |
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fabric
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| n.织物，织品，布；构造，结构，组织 | |
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entirely
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| ad.全部地，完整地；完全地，彻底地 | |
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rigid
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| adj.严格的，死板的；刚硬的，僵硬的 | |
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propellers
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| n.螺旋桨，推进器( propeller的名词复数 ) | |
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propeller
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| n.螺旋桨，推进器 | |
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motive
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| n.动机，目的；adv.发动的，运动的 | |
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fins
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| [医]散热片；鱼鳍；飞边；鸭掌 | |
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thoroughly
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| adv.完全地，彻底地，十足地 | |
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ascertain
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| vt.发现，确定，查明，弄清 | |
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acting
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| n.演戏，行为，假装；adj.代理的，临时的，演出用的 | |
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ascents
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| n.上升( ascent的名词复数 )；（身份、地位等的）提高；上坡路；攀登 | |
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aeronautical
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| adj.航空（学）的 | |
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enthusiasts
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| n.热心人，热衷者( enthusiast的名词复数 ) | |
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diverging
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| 分开( diverge的现在分词 )； 偏离； 分歧； 分道扬镳 | |
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pointed
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| adj.尖的，直截了当的 | |
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triangular
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| adj.三角（形）的，三者间的 | |
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vertically
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| adv.垂直地 | |
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slung
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| 抛( sling的过去式和过去分词 )； 吊挂； 遣送； 押往 | |
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boiler
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| n.锅炉；煮器(壶，锅等) | |
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41
attained
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| （通常经过努力）实现( attain的过去式和过去分词 )； 达到； 获得； 达到（某年龄、水平、状况） | |
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42
attain
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| vt.达到，获得，完成 | |
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43
specially
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| adv.特定地；特殊地；明确地 | |
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44
stiffening
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| n. (使衣服等)变硬的材料, 硬化 动词stiffen的现在分词形式 | |
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45
vessel
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| n.船舶；容器，器皿；管，导管，血管 | |
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46
descend
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| vt./vi.传下来，下来，下降 | |
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47
tilted
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| v. 倾斜的 | |
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48
upwards
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| adv.向上，在更高处...以上 | |
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49
boilers
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| 锅炉，烧水器，水壶( boiler的名词复数 ) | |
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50
vessels
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| n.血管( vessel的名词复数 )；船；容器；（具有特殊品质或接受特殊品质的）人 | |
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51
revolved
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| v.（使）旋转( revolve的过去式和过去分词 )；细想 | |
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52
forerunner
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| n.前身，先驱（者），预兆，祖先 | |
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53
cylinders
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| n.圆筒( cylinder的名词复数 )；圆柱；汽缸；（尤指用作容器的）圆筒状物 | |
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54
fully
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| adv.完全地，全部地，彻底地；充分地 | |
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55
inflated
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| adj.（价格）飞涨的；（通货）膨胀的；言过其实的；充了气的v.使充气（于轮胎、气球等）( inflate的过去式和过去分词 )；（使）膨胀；（使）通货膨胀；物价上涨 | |
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56
combustion
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| n.燃烧；氧化；骚动 | |
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57
previously
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| adv.以前，先前（地） | |
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58
varnished
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| 浸渍过的，涂漆的 | |
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59
torpedo
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| n.水雷，地雷；v.用鱼雷破坏 | |
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60
counteracted
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| 对抗，抵消( counteract的过去式 ) | |
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61
rendering
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| n.表现，描写 | |
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62
obviate
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| v.除去，排除，避免，预防 | |
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63
determined
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| adj.坚定的；有决心的 | |
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64
unevenly
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| adv.不均匀的 | |
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65
aluminium
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| n.铝 (=aluminum) | |
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66
insufficient
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| adj.(for，of)不足的，不够的 | |
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67
descended
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| a.为...后裔的，出身于...的 | |
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68
contemplated
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| adj. 预期的 动词contemplate的过去分词形式 | |
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69
linen
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| n.亚麻布，亚麻线，亚麻制品；adj.亚麻布制的，亚麻的 | |
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70
withdrawn
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| vt.收回；使退出；vi.撤退，退出 | |
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71
retired
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| adj.隐退的，退休的，退役的 | |
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