Man’s original ascents into the air were made possible by hot-air and hydrogen balloons
IT was probably the fact of having been born into a paper-making family that enabled two young Frenchmen - the brothers Montgolfier - to translate into reality the centuries-old dream of flight. Having begun their experiments with paper bags held over a fire, they progressed until they saw their balloon ascend with the world’s first aeronauts to make the pioneer voyage in the air.
THE MONTGOLFIER BROTHERS, who produced the first man-carrying balloon. On the left is Joseph, the elder, and on the right Etienne, who was five years younger. Although Joseph appears to have been the leading spirit, these French brothers worked so closely together in their balloon experiments that fame has honoured them equally.
The elder brother, Joseph Michel Montgolfier (1740-1810), appears to have been the leading spirit; but he worked so closely with Etienne Jacques Montgolfier (1745-99) that fame has honoured them equally. They were watching smoke rising in a chimney when they first discussed its “levity”, and speculated about the possibility of its lifting powers. It is known that their interest in such matters was stimulated by reading Experiments on Air, by Joseph Priestley, the Yorkshire scientist. The important part of their work began in 1782.
In November of that year they made a silk bag, open at the bottom, and burned paper under it. This bag, which had a capacity of about 40 cubic feet, became fully distended and rose to the ceiling. During outdoor experiments at Annonay, near Lyons, where they lived, the bag rose to a height of some 70 feet. A larger bag, of about 650 cubic feet capacity, was inflated over a fire of straw and wool, and this bag rose to an estimated height of 600 feet.
In the records of these early attempts with hot-air balloons a curious emphasis on the nature of the fuel used will often be noted. This was because it was believed that an unknown gas was being generated - a gas with novel lifting qualities. The term “Montgolfiers’ gas” was used for several years to describe the vapour rising from a fire of straw and wool. This fallacy persisted
until 1785, when the physicist de Saussure proved that Montgolfier balloons were merely hot-air balloons; they ascended because of the rarefaction of the heated air within them.
Early in June 1783 the brothers Montgolfier had advanced their experiments sufficiently to justify a demonstration in public. They used a spherical balloon made of linen sections which were buttoned together over a paper lining containing the heated air. The capacity of this balloon was approximately 23,430 cubic feet.
The demonstration was held in the market place of Annonay on June 5, 1783. It was a great success, for the balloon ascended some 6,000 feet and travelled nearly, one and a half miles from its starting point before it came down. This was the first public demonstration of a balloon ascent and, although no attempt had been made to carry a passenger on this occasion, the possibility of human ascent by means of a Montgolfier balloon had been foreshadowed.
The story of the new invention was the talk of Paris, whence it spread all over Europe, creating a sensation in learned and scientific circles. The Academie des Sciences prepared a report on the matter, but before this was issued in December 1783 the brothers Montgolfier had achieved further spectacular successes. As a prelude to human flight they decided to discover whether animals, unaccustomed to the rarefied atmosphere, would be injured at the heights attainable by their balloons. On September 19, 1783, in the presence of Louis XVI at Versailles a Montgolfier balloon was sent up with three living occupants in its wicker basket - a duck, a cock and a sheep. Their voyage lasted for eight minutes, when the balloon descended one and a half miles away, in the Forest of Vaucresson. A careful examination of the occupants of the wicker basket revealed that the only damage was a slight injury to the wing of the cock, such as might have been accounted for by a kick from the sheep.
The success of this experiment suggested that a balloon was capable of carrying a human passenger. Who would be the first man to try?
By the following month (October 1783) a new balloon had been completed and a volunteer was ready. The balloon was 74 feet high and 48 feet in diameter. The volunteer was J. F. Pilatre de Rozier, a young man holding office at the Royal Museum.
Attached to this balloon by cords was a light gallery capable of carrying several people, and encircling a space in which was arranged a fire. Fuel was available on the gallery and, by burning more or less fuel, the lift of the balloon was to some extent under control.
Confident of the balloon’s capabilities, Rozier persuaded the brothers Montgolfier to allow him to ascend in it; but so dangerous did the project appear that there was talk of withholding permission, and it was proposed instead that two criminals should be placed in the car of the balloon. Rozier was indignant at the idea of “such an honour being conferred on vile malefactors”. He remonstrated so forcefully that the opposition was withdrawn. It was judged imprudent to trust human life to a free balloon until the experiment of holding it with ropes had been tried. Rozier’s first ascent was on October 15, when the balloon was allowed to rise only to 80 feet; but four days later he ascended to more than 300 feet with the balloon held captive. He was convinced that he could make the first aerial voyage if the balloon were allowed its freedom.
About a month later his contention was proved. The balloon was taken to the gardens of the Chateau de la Muette, in the Bois de Boulogne, Paris, and was inflated during the morning of November 21, 1783. In the gallery with Rozier was a companion adventurer, the Marquis d’Arlandes. A little before 2 p.m. the balloon was released, and soared to a height of between 300 and 500 feet. Some twenty-five minutes later, after having travelled over Paris in a south-easterly direction, the two aeronauts landed safely.
A PRELUDE TO HUMAN FLIGHT was provided by a sheep, a duck and a cock being sent up in a basket. The object was to test whether the animals, unaccustomed to the rarefied atmosphere existing at a height would suffer any ill effects. In the old pictures reproduced on this page and the next, the balloon appears to have been drawn as a hydrogen balloon, although it was a Montgolfier hot-air balloon.
The distance they had travelled, over the River Seine and the dome of the Invalides, was only a little more than five and a half miles; but in making the first balloon voyage they had opened a new epoch. Man had learned to fly, and the conquest of the air had begun.
A full account of this historic balloon ascent is on record in two documents, one being a letter written by the Marquis d’Arlandes and the other a report by eight members of the Academie des Sciences. In his letter the marquis says: “I was surprised at the silence and absence of movement which our departure caused among the spectators, and believed them to be astonished and perhaps awed at the strange spectacle; they might well have reassured themselves. I was still gazing when M. Rozier cried to me:
“ ‘You are doing nothing, and the balloon is scarcely rising a fathom.’
“ ‘ Pardon me’, I answered, as I placed a bundle of straw upon the fire and slightly stirred it. Then I turned quickly, but we had already passed out of sight of La Muette. Astonished, I cast a glance towards the river. I perceived the confluence of the Oise. And naming the principal bends of the river by the places nearest them, I cried, ‘Passy, St. Germain, St. Denis, Sevres!’
“ ‘If you look at the river in that fashion you will be likely to bathe in it soon’, cried Rozier. ‘Some fire, my dear friend, some fire!’
“We travelled on; but, instead of crossing the river, as our direction seemed to indicate, we bore towards the Invalides, then returned upon the principal bends of the river, and travelled to above the barrier of La Conference, thus dodging about the river, but not crossing it.
“ ‘That river is very difficult to cross’, I remarked to my companion.
“ ‘So it seems’, he answered; ‘but you are doing nothing. I suppose it is because you are braver than I and don’t fear a tumble.’
“I stirred the fire. I seized a truss of straw with my fork; I raised it and threw it in the midst of the flames. An instant afterwards I felt myself lifted as it were into the heavens.”
The marquis then goes on to describe an incident that might easily have proved fatal. He heard two loud reports which he believed to be due to the cracking of cords in the balloon.
An examination of the envelope showed it to be burning in places, but he took a sponge - provided for the purpose - and with it extinguished the fire that fortunately was burning within his reach. Neither of the aeronauts seemed to have realized that if the fire had not yielded to this treatment their voyage would almost certainly have ended in disaster.
The final stages of this eventful ascent were accomplished without mishap. “I looked down”, says the marquis, “and it seemed to me we were going towards the towers of St. Sulpice, but on rising, a new current made us quit this direction and bear more to the south. I looked to the left and beheld a wood, which I believed to be that of the Luxembourg. We were traversing the boulevard, and I cried all at once:
“ ‘Get to the ground!’
“But the intrepid Rozier, who never lost his head, and who judged more surely than I, prevented me from attempting to descend. I then threw a bundle of straw on the fire. We rose again, and another current bore us to the left. We were now close to the ground, between two mills. As soon as we came near the earth I raised myself over the gallery, and, leaning there with my two hands, I felt the balloon pressing softly against my head. I pushed it back and leaped down to the ground.
“Looking round and expecting to see the balloon still distended, I was astonished to find it quite empty and flattened. On looking for Rozier, I saw him in his shirt sleeves creeping out from under the mass of canvas that had fallen over him. Before attempting to descend he had put off his coat and placed it in the basket. After a deal of trouble we were at last all right.”
A strange feature of this account of the first human ascent is that the marquis gives the date as October 21, 1783, instead of November 21. But his letter, which has every appearance of having been written soon after the event, is dated November 28, 1783; and the other authentic documentary record of the voyage - the report drawn up for the Academie des Sciences - gives the month as November. It is therefore generally supposed that the marquis wrote the word October in error.
There are two points of special interest in the report drawn up by the scientific observers of the Academie. It mentions that the aeronauts could have made a much longer voyage, for they still had the greater part of their fuel untouched when they landed; and one of its signatories was Benjamin Franklin, the American statesman and scientist. (A few years before Franklin had helped to draft the Declaration of Independence; a few years later he was to help to frame the new Constitution of the United States.)
THE RETURN OF THE ANIMALS produced consternation when the balloon landed - after a flight of eight minutes - in the Forest of Vaucresson, a mile and a half away from the start. The only damage to the animals was a slight injury to a wing of the cock, such as might have been caused by a kick from the sheep. In this contemporary drawing the balloon is shown still inflated, whereas a Montgolfier balloon would have collapsed on landing.
The success of this flight brought honours and decorations to the Montgolfier brothers. They had not only made the first balloon, but they had also had the honour of sending up the first aeronauts. The strangest feature of the achievement, however, was the fact that the Montgolfier balloon was outdated before it made its memorable ascent, for a better means of flight had already been successfully tried in Paris.
This rival invention was the hydrogen balloon. It had many advantages over the hot-air type developed by the brothers Montgolfier - advantages which later were to recommend it to all serious students of aeronautics, and to make it the precursor of the modern airship. Yet the hydrogen balloon failed to secure the honour of being the first vehicle of the air; that failure must be ascribed not to any merit of the rival hot-air balloon, but to the timely combination of courage, skill and enterprise with which the experiments with that inferior type were carried out.
The fundamental disadvantages of the hot-air balloon included its comparatively rapid loss of heat, the danger and difficulty of maintaining an open fire, and the limitations of lift which called for envelopes of unduly large volume. Despite these factors, many successful and noteworthy flights were made in various countries, until the increasing popularity of the hydrogen balloon indicated that this would be the type on which future development would depend. The first human ascent in a hydrogen balloon, also from Paris, took place within a fortnight of Rozier’s success in the hot-air balloon. Again the prelude to success was short, for the gas hydrogen had not been definitely isolated until 1766. Its discovery was due to the English physicist Henry Cavendish (1731-1810), who was following up the earlier investigations into the nature of air and gases by Boyle, Stahl, Black, Lavoisier and others.
Cavendish collected hydrogen by pouring sulphuric acid over iron filings. He noted that its specific gravity (or weight) was remarkably less than that of air, but as he was not concerned with the possibilities of lighter-than-air navigation, he did not suggest that hydrogen, if placed in a light spherical container, would raise the container and support it.
That proposal was first made by Dr. Joseph Black (1728-99), who in 1767 suggested that if a light bladder were filled with hydrogen, the bladder and its contents would form a mass lighter than air, and would therefore rise. Black even made preparations for an experiment on these lines, but they were never finished, and he later wrote of the matter as something which he had thought of as “merely amusing”.
The Italian scientist Tiberius Cavallo (1749-1809), who settled in England in 1771, demonstrated the lifting power of hydrogen ten years later. His experiment was simply to fill soap bubbles with the gas, and in his Treatise on the Nature and Properties of Air he recorded with what unusual rapidity the bubbles rose.
First Gaslight Balloon
The possibilities of hydrogen as a lifting agent were thus recognized before 1782, when the brothers Montgolfier began their successful experiments with the hot-air type of balloon.
Cavendish had stated that hydrogen had but one-fourteenth the weight of a given volume of air. Investigations by members of the Academie des Sciences in 1783 indicated that “Montgolfiers’ gas” was only of about half the weight of air; so the superiority of
hydrogen for aeronautical purposes seemed obvious. Under the auspices of the Academie, funds were raised for research, and the problem of generating hydrogen on a scale never before attempted was entrusted to the distinguished physicist J. A. C. Charles (1746-1823).
Charles was destined to make several fundamental improvements in the design of balloons. His early success was partly due to his association with two inventive mechanics, the brothers Robert, who devised a means of impregnating silk with rubber to make it impervious to gas. Their first gas-tight balloon was publicly demonstrated on August 27, 1783, when the balloon travelled from Paris to Gonesse, fifteen miles away, without a passenger.
RELEASING A HOT-AIR BALLOON made by the Montgolfier brothers in 1783. Straw and wool were used for fuel to heat the air, because, at the time, it was thought that these materials gave off some special form of gas when they were burnt. This fallacy persisted for several years, and the term “Montgolfiers’ gas” was commonly used to describe the vapour rising from a fire of straw and wool. Not until 1785 was it shown that the balloons rose because they were filled with rarefied air.
An interesting sidelight on the public attitude to aeronautics at that time is afforded by the fate of this balloon. When it fell among the peasants of Gonesse they were terrified, and armed themselves with flails and pitchforks. The sound and smell of the escaping gas held them back from it for a time, but when their fear had abated sufficiently they attacked the balloon and tore it to shreds.
Later, when searchers from Paris tried to find relics, scarcely a fragment of the balloon could be found. As a result the Government issued a notice entitled “Warning to the People on Kidnapping Air Balloons”. This document described the ascents made from Annonay and Paris, and explained the nature of the phenomena. It warned people not to be alarmed if they saw something like a black moon in the sky. Fear, it said, was unnecessary, as “the seeming monster is nothing more than a bag of silk filled with gas”.
Preparations for a larger hydrogen balloon, capable of carrying passengers, were immediately begun, and on December 1, 1783, Charles and the elder of the brothers, Robert, ascended from Paris and landed at Nesle, twenty-seven miles away. This was the first human ascent in a hydrogen balloon, the type that was destined to be the first reliable vehicle of the air.
From the beginning Charles seems to have appreciated all the fundamental problems connected with this type of aircraft. His earliest balloon embodied all the essential features found in the later types. He safeguarded the envelope against leakage, and covered it with a network of cords from which a light car was suspended: he carried a thermometer and barometer, made adequate provision for ballast, and even fitted a valve to the top of the bag.
This valve shows that he realized the necessity for reducing the pressure of the gas inside the envelope when the balloon rose to considerable altitudes. The external atmospheric pressure decreases with altitude, and Charles foresaw that without a safety valve the pressure inside the envelope might then increase to the point where it would burst the envelope.
His foresight stood him in good stead. During the flight with Robert he took a series of barometer readings which indicated an average height of 1,800 feet. Having reached Nesle, Robert left the balloon and Charles reascended alone. Relieved of the weight of one person, the balloon rose rapidly to 3,000 feet, and continued to ascend steadily.
Having placed the barometer and thermometer where he could read them without moving, he sat between them, with a watch and paper in his left hand, a pen and the cord of the safety valve in his right. “The balloon”, he wrote later, “which was quite flabby and soft when I ascended, was now taut, and fully distended. Soon the hydrogen gas began to escape in considerable quantities by the neck of the balloon, and then, from time to time, I pulled open the valve to give it two issues at once. ... I passed in ten minutes from the temperature of spring to that of winter.”
Charles ascended to 9,000 feet, becoming the first altitude record-breaker. He then descended scientifically by opening the valve as necessary, finally throwing out some ballast kept for the purpose of reducing the shock of landing.
In the higher altitudes he had experienced severe pain in the ears, which disappeared on descent. His record shows that he was keenly alive not only to the novelty of his situation, but also to the elation of travel by air. But he never repeated the experiment of a flight in person.
Charles was the first man to ascend alone in a free balloon; but his greater claim to aeronautical fame lies in his scientific attitude to the new problems.
Based on sound scientific principles, his hydrogen balloon proved its worth within a few days of Rozier’s ascent. It travelled approximately five times as far as the hot-air balloon in which Rozier and his companion had made the pioneer voyage of the air. If anything can enhance their achievement it is the fact that they used this imperfect means of ascent; for the historic importance of the hot-air type of balloon lies not in its principles, but in the courageous feat accomplished with it by the first aeronauts, Pilatre de Rozier and the Marquis d’Arlandes.
Only six years after Paris had witnessed these aerial voyages the French Revolution began in blood and terror. Many of those who played important parts in it must have seen, also, the balloon ascents which preceded it. Their impression of the experiments in aviation was doubtless dulled by their later experiences; and they can hardly have realized that those experiment heralded another revolution - perhaps of more significance than that which cost so many lives.
FIRST FREE MAN-CARRYING BALLOON in flight over Paris in 1783. With two men on board - J. F. Pilatre de Rozier and the Marquis d’Arlandes - this hot-air balloon rose to over 300 feet and travelled a distance of about five and a half miles. Some twenty-five minutes elapsed during the flight, which provided a thrill for the aeronauts when the fabric was set alight by the fire used to heat the air in the balloon.