How the Lightest Element on the Periodic Table Influenced the Dawn of Air Balloon Sailing
Jacques Alexandre César Charles (1746 - 1823) was a French inventor, scientist, and balloonist who — along with Robert brothers Anne-Jean (1758 - 1820 ) and Nicolas-Louis (1761 - 1828) — launched the world‘s first (unmanned) hydrogen-filled balloon in August 1783.
Though Charles was initially employed as a clerk at the Parisian Ministry of Finance, he was inspired to pursue scientific investigation by the work of contemporary scientists, such as Henry Cavendish (1731 - 1810), Joseph Black (1728 - 1799) and Tiberius Cavallo (1749 - 1809).
But, most of all, he was allegedly inspired by the work of natural philosopher and theological writer Robert Boyle (1627 - 1691), and Boyle‘s Law (also known as Mariotte’s Law) in particular, which explored the relationship between pressure and volume.
At the time, scientists investigated the relationships among the pressure of a gas (P) and its temperature (T), volume (V), and amount (n) by holding two of the four variables constant, varying a third, and measuring the effect of the change on the fourth.
So, in 1662, Boyle focused his attention on the understanding of the empirical relationship pertaining to the pressure (P) and the volume (V) of a confined gas held at a constant temperature. He found that the density of gas varies inversely with its volume.
In other words, “as the pressure on a gas increases, the volume of the gas decreases because the gas particles are forced closer together. Conversely, as the pressure on a gas decreases, the gas volume increases because the gas particles can now move farther apart.”
Furthermore, while he was experimenting with iron and acids, Boyle successfully produced hydrogen gas in 1671, though it wasn't until 1766 that Henry Cavendish (1731 - 1810) recognized it as a distinct element. Still, the discovery of hydrogen proved to be a game changer.
In 1787, Charles took the idea and built on it, formulating his own law. It suggests that the volume [V] occupied by a fixed amount of gas is directly proportional to its absolute temperature [T], if the pressure remains constant. He also realized that gasses expand when they’re heated.
Hot air is less dense than cold air, therefore it rises. Hydrogen is the lightest element on the periodic table, which makes it a suitable lifting agent for a balloon. So, teaming up with the Robert brothers, Charles proceeded to test if, in fact, hydrogen would successfully lift a mass.
Working out of a workshop at the Place des Victoires in Paris, the brothers managed to invent the methodology for the lightweight, airtight gas bag by dissolving rubber in a solution of turpentine and varnishing the silk sheets, which were stitched together, to make the main shell.
The final product was a sphere measuring 35 cubic meters. To fill it with hydrogen gas, half a ton of sulphuric acid was poured onto a half a ton of scrap metal. The gas was then fed into the balloon via lead pipes — a difficult process, as the gas was not passed through cold water.
The world’s first documented hydrogen-filled balloon, capable of lifting roughly 9 kg, was launched by the team on August 27th, 1783, where the Eiffel Tower stands today. It traveled northwards for 45 minutes and landed 21 kilometers away, in the village of Gonosse.
Clearly, the massive floating balloon took the residents of Gonosse by surprise. Prepared to defend their home against all kinds of invaders, including airborne ones, they attacked their perceived foe with knives and pitchforks. In Paris, though, it made a different impression.
The event and the days leading up to it were a massive spectacle. Daily progress reports about the inflation of the balloon drew a crowd that seemed to grow every time there was an update; the balloon itself was secretly moved to the launch site — 4 kilometers away — the night before.
Benjamin Franklin (1706 - 1790) was among the crowd of onlookers on the day of the event. According to different sources, when someone asked him about the supposed purpose for the new invention, he answered with the counter question: “What purpose does a newborn child have?“
Thrilled with the outcome, Charles and the Robert brothers, prepared to get on with their next thing: manned flight. They set the date for four months later, and, on December 1st, 1783, Charles and his co-pilot Nicolas-Louis ascended to a height of about 500 meters.
Theirs, however, was not the first manned flight in history. On September 19, 1783, the Montgolfier brothers — Joseph-Michel (1740 - 1810) and Jacques-Étienne (1745 - 1799) — launched history’s first hot air balloon, boarded by animals, which lasted for eight minutes.
Since the animals survived, a manned flight was cleared for takeoff. So, on November 21st, 1783, physicist Jean-François Pilâtre de Rozier (1754 - 1785) and officer François d’Arlandes (1742 - 1809) successfully flew for 25 minutes, becoming the first confirmed human airmen.
This, however, did not deter Charles and the Robert brothers. Aside from making their flight ten days later, which lasted for two hours, Charles took the accomplishment one step further by ascending again, alone, making him the first airman to travel solo.
It took almost three days to produce the necessary hydrogen gas from iron filings and sulfuric acid to make the flights last. But the effort allowed the duo to travel 36 kilometers, to the village of Nesles-la-Vallée, as well as to make two flights in a single day.
During the flight, “he had a barometer and a thermometer on board. With the help of the former, he was able to determine that his greatest altitude reached was 3467 m.” The accomplishment also meant that Charles was able to prove that the smoke was not what caused hot air balloons to lift.
Though Charles and the Robert brothers pioneered the use of hydrogen for lift, the Montgolfier brothers invented the first hot air balloons; as such, hydrogen-filled balloons are called Charlières, and hot air balloons are referred to as Montgolfières, respectively.
Together, the various parties involved in the pioneering of flight continued their scientific investigations for years to come. Charles and the Robert brothers built an elongated, steerable craft that incorporated internal ballonnet (air cells), a rudder, and a method of propulsion.
Though Charles never got a chance to fly it, he did develop a number of impressive and useful inventions, one of which was a valve for letting hydrogen out of the balloon. In addition to conceiving his law, he also confirmed Benjamin Franklin’s electrical experiments.
As for the Montgolfier brothers, Joseph Michel automated the pulsation engine, creating an autonomously operating water pump, the hydraulic ram; Jacques Étienne Montgolfier later founded the first vocational school for papermakers.