Two French papermakers from Annonay near Lyons, Joseph and Etiennne Montgolfier first demonstrated their experiments with hot air balloon flight in June 1783. Constructed of paper-lined linen, the unmanned balloon obtained lift from hot air, which rises because it is slightly less dense than cold air. Buming straw, wool and various odd substances in a basket slung beneath the open base of the bat loon envelope produced the heat..

Initially, the Montgolfiers did not appreciate why their invention had worked, thinking the combination of materials in their fire had produced a lighter-than-air gas. The problem with hot air balloons is that the difference between the densities of hot and cold air is not that great. A large balloon envelope would be required to lift the fire, passengers and ballast.

In the same year, French physicist Jacques Charles invented the gas balloon. His balloon, the 'Charlieres', used hydrogen (the lightest element, discovered in 1766) to lift a sealed envelope. This had an outer cover to which to a gondola was attached by lines. The first model was just 12ft in diameter. Unmanned, in three-quarters of an hour it flew 15 miles before landing near a remote village. Pitchforks in hand, the local peasants ran out to attack what they believed to be some devil-created machine.

First Passengers

Not to be outdone, the Montgolfiers continued their experiments. That September at Versailles, a duck, a rooster and a sheep were sent aloft to see if the rarefied air would harm them. The only damage was to the rooster's wing, which was probably kicked by the sheep.

Two months later, on 21 November, Pilatre de Rozier and the Marquis d'Arlandes rose from the gardens of La Muette, near Paris, to make the first manned flight. The balloon, open at the base of the envelope like modern leisure balloons, had a platform slung beneath it. In the middle of this platform burned a fire to heat the air, which they now appreciated to be the source of the balloon's 'lift'.

The passengers were in a circular gallery fitted around the platform. The flames from an auxiliary brazier got fierce as the Marquis replenished it with straw bundles until a few cinders struck the balloon, which began to smoulder. Fortunately, the two aeronauts were prepared for this and doused the flames with wet sponges. Half an hour and 6 miles later, they landed.

The inherent dangers of the hot-air design were obvious and it was to be Charles' design that became pre-eminent and developed into the first military balloons. Just a fortnight after de Rozier's flight, Charles and a Monsieur Robert took to the air in a hydrogen balloon, flying 27 miles before Charles dropped Robert off and ascended again.

Although he never flew again, Charles began experimenting with vents for better vertical control and other suggestions were put forward for steering a balloon in flight.

In January 1785, a hydrogen-filled balloon carried Jean-Pierre Blanchard and Dr. John Jefferies from Dover to Calais in the first air crossing of the Channel. De Rozier meanwhile, continued his own experiments. One of these was an attempt to mix air with the highly flammable hydrogen gas. His airship consisted of a cylindrical hot-air envelope with a spherical gas container above.

First Casualty

The purpose of this combination was to remove the need for ballast: The hydrogen would keep the balloon aloft, while its height could be varied by heating the air. He also planned to cross the Channel, but perhaps inevitably, during the trials the craft exploded into flames. De Rozier was thus both the first aeronaut and the first victim of air travel.

While this incident discouraged many, an Italian Count Zambeccari tried to refine the hot air design by heating the air in the envelope with a heater fuelled by spirit. This was an early version of the gas burner seen on modern balloons. Setting out on one flight, the balloon became entangled in a tree, causing the hot spirit to spill over the pilot, setting light to his clothes.

However, the sudden burst of flame lifted the balloon clear of the tree and Zambeccari managed to extinguish the flames and descend safely. For the next decade, the dangers of ballooning restricted it to being a popular toy.

At the end of the 1780s, the first extensive technical investigations were being conducted by General Meusnier, who wrote the 'First Great Technical Manual of Aeronautics'. This did not contain any references to military applications. He would not see the start of military ballooning as he died on 13 June 1793, just as the Convention in Paris approved an idea of balloons being used for reconnaissance. This was put forward by a Chemist of the Dijon Academy, Guyton de Morveau. An eight-man commission, whose members included Carnot. was established to consider the idea more carefully.

Steering

The real problem with balloons was that they could not be controlled sufficiently in flight for effective reconnaissance. Vincent Lunardi, who had made the first flights in England, used oars in an effort to control the direction of flight, but to no avail. Blanchard's cross-Channel balloon had carried wings, which proved equally useless.

The most bizarre idea came from Kaiserer, who in 1801, suggested tethering a team of eagles to the balloon. However, as the first balloons took to the air, the basis of a solution was provided by Jean Baptiste Meusnier, who in 1784 produced the first design for a dirigible, (a steerable airship). This utilised a balloon shape similar to the familiar flattened cigar with pointed ends, propellers for power and a rudder. Although it was never built and human power for the propellers would have only moved it at a very slow speed, it bears a close resemblance to the airships of the early 20th century.

Guyton's Balloons

Back in the real world, Guyton therefore proposed the use of a balloon tethered by lines to the ground. This not only controlled the balloon, but largely prevented the natural tendency of a spherical balloon to spin in flight. Interior Minister Gartat came up with the necessary money and materials.

On 26 July 1793 Guyton officially informed the committee that he had constructed a test balloon, based on an example found in the confiscated property of the Emigre, L'Allemand-Saint-Croix. Further efforts were made to provide a steering mechanism and the first trial for Morveau's ideas was conducted at the siege of Conde in the summer of 1793. A small untethered 'pilot balloon' was deployed to overfly enemy positions carrying messages.

However, the material used for the envelope was not thick enough and the balloon deflated, sinking behind enemy lines into the hands of the Allied commander, Coburg. It carried a pigeon for the return flight, which was duly consumed by allied soldiers. It was thus concluded that only a tethered balloon was feasible and further tests were conducted on this basis, despite the disadvantage of observers having to look at enemy lines from a distance.

Still keen to push their alternative free-flying design, at the end of 1793 one of the Montgolfiers proposed that a large balloon be constructed. This would carry a 30-ton explosive which could then be dropped on the besieged port of Toulon.

Manufacture

Although that idea was rejected, doubts continued over the hydrogen balloon. Charles had shown that hydrogen was the best gas because it is the lightest element. The main technical problem to be overcome before the balloon could enter service was filling the huge envelope with hydrogen.

The sulphuric acid (required to separate water into its constituent elements of hydrogen and oxygen) was in very short supply. Sulphur was rare in France and was usually requisitioned for the manufacture of gunpowder. However, Lavoisier's discovery that water could be separated using red-hot iron came to Guyton's rescue, particularly as it made large-scale production feasible.

After gaining government approval, the Paris physicist Jean Coutelle was authorised to conduct the project. Working with the famous technician, Conte, he refined the process so that a balloon was filled in front of the commission at the Tuillieres in Paris.

The hydrogen was produced in a brick oven, in which a cast iron tube, measuring 1 metre by 30cm diameter within 30mm thick metal. This was filled with scrap metal, nails and iron filings and was heated until it glowed red hot. At both ends, which tapered into a smaller rounded shape, were fixed small pieces of sheet iron, later copper tubing. At one end, water was poured into the small tube and conducted through the pipe system across the glowing irons while, at the other end, the hydrogen was collected as it boiled off.

Further trials went well and on 25 October, the Committee For Public Safety, (the Revolutionary government), ordered the construction of a fixed balloon and gondola to lift two men, observation equipment and ballast.

Armee Du Nord

The first balloon was to go as quickly as possible to the Armee du Nord, while St. Croix's old balloon was also repaired and refurbished. In the meantime, Guyton had developed a manual for the use of balloons, including a signalling system. This system, which was used throughout their existence by the balloon companies, consisted of a series of light signals and red, yellow and green flags.

Notes could also be dropped in weighted bags but, at low altitudes, a 'voice tubes was used. By combining signals and firing shots from the ground, two-way communication could be used - for example: 4 shots meant that 'The garrison will make a foray'.

Four balloons, each with an envelope 10m in diameter, were constructed of varnished silk. Each was covered with a restraining net, from which a basket was slung. The balloons were named the Entreprenant, the Celeste, the Telemarque and the Intrepide.

The problem with the envelope's material strength was also addressed by the application of linseed oil to reinforce the fabric. At the base of the balloon envelope, a tie-pull rope was attached for the release of gas to allow the balloon to descend.

In October 1793, the balloon sent to the Armee du Nord was intended to be deployed in the relief of Mauberge, then besieged by Allied armies. Coutelle was sent on ahead to prepare the requisite gas-producing ovens and other materials, as well as informing Jourdan of the balloon's despatch.

By now, it was the end of the campaigning season and bad weather was closing in. Combined with the heavy expense, the National Assembly's Political Commissar attached to the Nord took the view that the idea was silly and threatened to have Coutelle shot. Quite naturally in the political climate of 'The Terror', Coutelle rushed back to Paris to stop the balloon's transport.

The Meudon Base

The French government however decided to pursue the project. St. Croix's balloon was sent for further tests at Meudon, (southwest of Paris), where a research facility had been authorised to experiment with pyrotechnics and experimental weaponry. The now Captains Coutelle and Lhomond, later joined by Conte, were authorised to establish the first 'aeronautical Test Station'.

Work continued on tests of materials and gas production all through the winter of 1793-4. On the 27 March, St. Croix's balloon, now the Empreveur, was filled with 350 m3 of gas, a process that took 10 hours. Two days later, it flew for the first time. Coutelle went up in person to a height above 1500 ft and gave an enthusiastic report about the view he had.

Tests at Meudon showed that on a clear day at about 500m, (1600 ft.), with a telescope, it was possible to see in detail terrain features and troops at 9-10 kms. At 17-22 kms, it was still possible to see clouds of smoke and the general lines of the terrain. As a result, the Premiere Compagnie d'Aerostiers Militaire (1 st Military Airship Company) was formed, expected to comprise a Captain, a Lieutenant, a Sergeant-Major, a Sergeant, 2 Corporals and 20 men, without exception all skilled artisans.

Uniforms

Their uniforms were blue shirts and trousers, black cuffs with red piping, wrth infantry buttons imprinted with 'Aerostiers'. They wore tricornes and were armed with a short sabre and two pistols. They also had a workcoat made of blue or bleached twill cloth. Officially, as skilled men, they had the status of engineers.

Further trials at Meudon showed once inflated a balloon could stay usable for up to two months before requiring replacement gas, but the actual production of the hydrogen gas remained a torturous process.

A brick oven had to be constructed, in which 7 cast-iron tubes were placed. These were filled with iron filings and scrap iron free of rust, four on the bottom and three on top, tapered off at each end to narrow copper pipes. More bricks were then used to close off the oven. At one end, an upturned water tub poured water down the small feeder pipes into the main tubes. The oven was heated up with charcoal until the rods glowed red hot.

The hydrogen boiled off and the pressure forced the water into a second square tub at the other end, which was filled with saturated slaked lime solution. The gas streamed through this solution and was then purified by passing it through a carbon filter to extract any oxygen impurity. The pressure then pushed it on through a rubber tube into the balloon at the other end, which steadily inflated as the gas entered.

The extraction of enough hydrogen gas (524 m3) from water to inflate the balloon was a slow process. The fire had to act equally on all the rods, with great care having to be taken that there was no cracking or swelling, otherwise no gas would be produced.

If the gas was escaping a blue flame became visible, which then had to be plugged - a tricky business when the whole apparatus was red-hot. The actual inflation could take 36-40 hours, during which time the equipment could not be left unattended. The biggest problem was therefore that a deflated balloon could probably not be inflated and deployed at a battle site before the fighting was finished.

The support train comprised nine heavy four-horse transports, including the two equipment-wagons and a baggage cart. It hauled seven cast iron tubes, a number of barrels full of scrap iron and a heavy balloon cover, a total weight of 17,000 pounds.

The balloon could easily carry two people and 120-140 pounds of ballast - sand or earth in linen or canvas sacks. Lines attached the gondola to the securing net strung over the top of the balloon envelope, to which two stouter lines were also attached to connect the balloon with the ground team. These ropes were roughly 400m long and could if necessary be extended to 1800m.

The French balloon finally made its way to war in mid-1794 with Coutelle now formally appointed to the command of the 1 st Company. Under-strength at just 26 officers and men, who had received little training, they reached Mauberge, near the border with the Austrian Netherlands (Belgium), with the 'Entreprenant' on 6 May 1794.

A gas kiln was built and the balloon inflated, the process taking 50 hours. For the next three weeks, a few trial ascents were made. Then at about 7.00 p.m. on 2 June, 'Entreprenant' rose for its first proper flight to 350m above Mauberge, from where its two crew were able to give an extensive report on the troop positions around the city.

The Austrians thought at first that this was a student prank, but noted the crew could be seen using a red and a white (presumably yellow) flag. Technical work meant that the balloon was not available for use at the following day's battle at Gosselies, as it was not possible to move it at least some of the 39 km from Mauberge.

Two Flights Day

Nevertheless, from 3 to 21 June, there were usually two flights a day in the area, the balloon always on tethered lines, including during the first clash at Fleurus on the 16th. Later, from the 20th onwards, its crew could observe the advancing Austrian columns as Coburg mounted his counter-attack. The balloon's effectiveness was however greatly reduced by its being positioned too far from the fighting.

The problem was not helped by the observers' lack of experience, especially when the balloon basket both swayed and wobbled vertically in the wind. Military aviation was also rapidly becoming dangerous - on the 13th, an Austrian battery tried to open fire on the balloon.

This occurred every subsequent day with 4 pounders turned on it. As the 'Entreprenant' ascended to 200m on the 21st, Austrian fire reached to within 40m, but the balloon ascended farther to gain protection in the fog. Although the balloon was never hit, this high angle fire was more worrying for the men on the ground holding the lines, as the cannonballs returned to earth.

The real problem was bad weather, which one time dragged the 'Entreprenant' on to the church tower at Mauberge, where it suffered minor damage as a result. The gas oven also suffered problems with some of the retort external tubing melting, causing major delays in gas production. On the 21st, General Jourdan, commanding the Sambre-Meuse Army ordered Coutelle's company towards Fleurus, some 30 miles (50 km) away, where he expected to clash with the Imperial army again in the next few days.

Dispatched to Charleroi, 34 km away, the balloon had to be moved in a fully inflated state because Jourdan needed news from that sector as soon as possible.

Crossing Obstacles

Accompanied by a cavalry escort, it set off tethered to a horsedrawn wagon, but the first problem was to pass through the city gate of Mauberge. Guyton proposed to cross the wall at night. He would abandon the cart and tie the ropes from the balloon to the 20 mounted men who formed the escort, leaving a man aboard to control the ballast.

By gradually transferring the ropes from the cart to the cavalrymen, the obstacle was passed and the march continued through the night of 22nd-23rd. The balloon maintained at a height such that cavalry and transports could pass beneath it. The effect of this on the horses is not recorded.

The 'Entreprenant' reached Charleroi the following day, the 25th, just as the fortress was captured from the Allies. It was aloft on 26 June 1794 throughout most of the battle of Fleurus from 6.00 a.m. to 4.00 p.m. In the first use of aviation in battle, Coutelle was in the gon dola during the fighting supplying information, which is said to have assisted Jourdan to defeat the Austrians.

Unfortunately, the reports about its effectiveness in confirming Austrian movements were later lost, but Jourdan's later report in 1799 was instrumental in leading to the disbandment of the force. Soult and Championnet also said it served no real purpose, although it may have caused some consternation in the Austrian ranks.

Much of the fighting led by the Austrian left under Archduke Charles and Beaulieu took place around Charleroi in broken terrain where the actual army lines flowed continuously. The reason why the French won the battle of Fleurus was largely due the nerve of the Allied commander, Coburg, failing at the crucial moment, not that Jourdan derived some intelligence advantage from his balloon.

On 5 July, after 27 flights and suffering from the heat and several rainstorms, the balloon was greatly weakened and suffered heavy damage in a storm. All these flights had been on the original gas, which was gradually seeping out of the envelope, so it was sent back to Mauberge for repair.

Napoleonic Balloons (Part 2)