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How often has aviation defined the leading edge of science? Discovery of the speed of sound is an obvious example, as it was necessary to break the Sound Barrier in order to understand it. If I asked you for the first names of the two brothers who invented the first successful manned aircraft, and you answered Orville and Wilbur, you would be off by 120 years. Joseph and Etienne Montgolfier invented the first reusable manned aircraft in 1783, a hot air balloon. The brothers believed that their lift was coming from smoke, which they could clearly see rising in the air.
If I asked you for the first names of the two brothers who invented the first successful manned aircraft, and you answered Orville and Wilbur, you would be off by 120 years.
Ben Franklin, a world class scientist, was in Paris negotiating the end of our War of Independence, and witnessed the first flights of two different types of aircraft. In letters to an English scientist, Sir Joseph Banks, dated December 1, 1783 and January 16, 1784, he described the balloon, and attributed the lift to “air rarified by heat”. If you wonder why he was describing the technology to scientists in a nation with which we were still at war, it was because he thought that aviation offered the opportunity for “convincing sovereigns of the folly of wars”.
The source of lift of a hot air balloon can be explained by laws of physics and chemistry, respectively Archimedes’ Law and Charles’ Law.
The actual source of lift of a hot air balloon can be explained by laws of physics and chemistry, respectively Archimedes’ Law and Charles’ Law. While Archimedes’ Law was known for 2,000 years, Charles’ Law would not be published until 1802. Clearly, the timing of the latter supports the ‘leading edge of science’ designation.
Archimedes’ Law: An object floating on or immersed in a fluid will be buoyed up by the weight of the displaced fluid.
Charles’ Law: An ideal gas will expand in direct proportion to its absolute temperature.
So, Ben Franklin’s analysis was pretty accurate, although without the precise numbers. Thus, the first manned aircraft preceded publication of the enabling law of chemistry. Using the same law, you would conclude that a football pumped to a specific pressure in a warm room will have lower pressure out in a cold field. (Surprisingly, not one journalist mentioned this during the ‘Inflation-gate’ controversy!)
What caught my attention as a chemist was that Jacques Charles was also in the race to invent the first manned aircraft. Yes, it was the same Charles. His balloon, which flew just two weeks after the Montgolfier balloon, got its lift from hydrogen, aided of course by Archimedes’ Law. Hydrogen was newly discovered at the time, and Charles called it “inflammable air”. He did not know what it was, but he knew how to make it, and knew that it was lighter than air. Bottom line, the role of hydrogen in producing lift was explained by another of the Ideal Gas Laws, Avogadro’s Law, which would not be published until 1812. It states that ‘At constant temperature and pressure, equal volumes of ideal gases contain the same number of molecules’. Once again, invention of a new type of aircraft—a hydrogen balloon—preceded publication of its underlying science.
The molecular weight of hydrogen gas is two, whereas that of nitrogen is 28 and oxygen is 32. A cubic foot of air weighs slightly more than 14 times the weight of a cubic foot of hydrogen. If you want to go deeper with this, humid air is lighter than dry air (i.e. higher density altitude), because water molecules (molecular weight = 18) displace either nitrogen or oxygen molecules. Enough with the science, what was really happening in those days?
Joseph and Etienne called their balloon the Montgolfiere, which flew for the first time in September 1783, but it was still tethered to the ground. The first free flight was the following month with three ‘test pilots’: a duck, a rooster, and a sheep. The duck clearly could fly, so flight would not kill it. The rooster looked like it could fly, but rarely did. Therefore, its chances were good. The sheep clearly could not fly. If it survived, so could a man. One can only speculate that people on the ground were surprised when a huge UFO flew over them piloted by an equally terrified sheep baaing. Klingons or Vulcans probably did not come to mind. Witches were more likely.
In any event, the Montgolfier brothers were still chicken, and petitioned the king of France for the loan of two condemned criminals to use as human test pilots. Pilatre de Roziere, who had gone up in the tethered balloon in September freaked out. “You can’t give the honor of being the first aeronaut to a condemned criminal!”
He won the argument, and the king had to be told. For some reason, Louis XVI insisted that his cousin, the Marquis d’Arlandes be part of the crew. Perhaps he didn’t like him.
Meanwhile in the other camp, Charles had managed to fill a balloon with hydrogen. Unfortunately, it got away from him and came down in the village of Gonesse, terrifying the inhabitants. Whether or not they had heard about flying sheep, I can’t say. But a huge UFO dropping from the sky got the expected response. They tore it apart, and could not understand why it was just skin. No insides. That set Charles back, and he had to make more inflammable air and another balloon, which he ensnared under a fishing net this time. So, the Montgolfiere won the race to be the first manned aircraft.
Charles was onboard with Nicholas Robert when his hydrogen balloon made its first flight on December 1, 1783. The Charlière flew farther, higher, and longer than the Montgolfiere had done two weeks earlier. When they eventually touched down, Nicholas Robert got out, and the balloon immediately went up again, making Charles the first man to fly solo.
Pilatre de Roziere should be listed among the test pilot elite. Two years after the first flight he attempted to fly across the English Channel in a type of balloon now known as a Rozière, a balloon with two separate bags, one inside the other. The outer bag is filled with heated air, whereas the sealed inner bag can contain either helium or hydrogen. In 1999 a Rozière called the Breitling Orbiter made the first nonstop flight around the globe. Its inner bag contained helium, which is an inert gas. Not so with the original Rozière, which had a bag of hydrogen inside a bag of air heated by burning straw in a frame at the bottom. One would think that the name—‘inflammable air’—might have given him some pause. He died when it blew up at an altitude of 3,000’ AGL. The leading edge of science can be dangerous.
Boyle’s Law (1662) was actually the first of the three laws that became known as the Ideal Gas Laws, the other two being the already described Avogadro’s and Charles’ Laws. It states that the absolute pressure of an ideal gas is inversely proportional to the volume it occupies. While that may seem obvious to us today, it triggered the transition from alchemy to chemistry in the 17th century. It is also central to the modern concept of COSH, which stands for Control of Static Heaviness, and is used in modern VTOL airships such as Airlander and Aeroscraft. COSH controls buoyancy by a method similar to ballast tanks in a submarine, except that ambient air is used in place of sea water and compressed helium instead of compressed air. Buoyancy is achieved by releasing helium into bags that expand, thereby displacing air which is heavier. Compressing some He back into high pressure tanks shrinks the bags, allowing ambient air to flow back into the empty space, thereby making the airship heavier again.
COSH, which stands for Control of Static Heaviness, is used in modern VTOL airships such as Airlander.
COSH overcomes one of the major disadvantages of Zeppelins. While great at going up and staying aloft, their huge size and lightness created problems when landing or docking. Without control over buoyancy (i.e. “static heaviness”), any large cargo that was off-loaded had to be immediately replaced with something of equal weight or the lift gas had to be vented.
Airships using COSH can also stay aloft indefinitely, but they can land vertically anywhere with enough clearance. Patents have already been issued to Amazon and Walmart for airborne warehouses to be serviced by drones. While this use of COSH is clearly leading edge, the underlying sciences are not.
- Aviation at the leading edge of science - September 11, 2024
- Passing the torch - July 22, 2024
- Pilots are not smarter, they are just better prepared - May 17, 2023
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