Flying Without Moving

Stelios Mores on the history and physics of flying. Plus a fun experiment for young scientists.

Supermarine Spitfire.jpg


On 21 November 2018, aeronautical engineers at the Massachusetts Institute of Technology demonstrated what has for many years been the stuff of science fiction. The first-ever aircraft to be driven without any moving parts was being propelled by an 'ion drive', which creates an electro-aerodynamic thrust or an 'ionic wind'. The environmental benefits of a silent aircraft engine which uses electricity alone to accelerate the air around it without any emissions and with the potential of using renewable energy, is perhaps the technology which many in the air transportation industry were hoping for.

Flight has played a major part in religions and the myths of early civilisations. Protagonists have often paid the ultimate price, much like in the famous story of Dedalus and Icarus. Unheeded by these warnings of impending doom, the Chinese philosopher Mo Di went on to invent the first kite as early as the fifth century BC and subsequently the kite was used to lift people into the air. A century later Chinese children were playing with toys which had a pair of feathers at the end of a stick that would take off when spun rapidly, and festivities saw the advent of the Sky Lantern which relied on a lightweight burning lamp heating up the air inside a paper chute to make it rise. Despite these early advances, flight was to remain a passive endeavour for over two millennia, requiring high jumping off points and relying on convective currents in the atmosphere. 

Powered flight with all its implications was an altogether different challenge. The first attempts at understanding the mechanisms of flight were made by Roger Bacon who during the 13th century suggested that air had an upper surface, such that a suitable apparatus might float on it as a ship floats upon the surface of the sea. Over two centuries later Leonardo da Vinci used his knowledge of the natural world and avian anatomy to design flying machines including the Ornithopter with flapping wings and a type of helicopter. In the 1670s, the Jesuit priest Francesco Lana described a ship which incorporated four giant evacuated copper spheres which would make the ship lighter than the air around it. This idea of a lighter than air vessel led to the development of the first-ever hot air balloon by the French brothers Joseph-Michel and Jacques-Etienne Montgolfier in the early 1780s. Initially the design relied on a ground-based coal burner to heat up the air and make the balloon rise, but this was soon suspended directly below the envelope allowing it to fly much greater distances. Within a decade, what was initially a public curiosity had become an established form of transport. The subsequent development of dirigible balloons led to improvements in steering and control. By 1785, the Frenchman Jean-Pierre Blanchard and the American John Jefferies had flown across the English Channel in such a craft. 

In 1852 Henry Giffard replaced the hot air with hydrogen gas resulting in an almost thirtyfold improvement in lift for an equivalent volume, allowing far heavier loads to be lifted. The cloth-like exterior of the gas envelope was replaced with a harder, stiffer fabric and frame, and incorporated various propulsion systems such as paddles, wings and rudders. Having first been driven by steam, the airship propellers of the late 1800s were powered by batteries and electric motors. The early 1900s saw German Graf Zeppelin airships take to the skies lifting luxury gondolas for fare-paying passengers, oftentimes travelling for periods of many weeks as they flew across the Atlantic from Central Europe to South America. In time the hydrogen was replaced with safer helium.

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During this same period significant advances in powered flight were also being made with the commercial gains which this implied. In 1874 Felix du Temple developed a steam-powered aircraft capable of taking off and making short gravity assisted jumps from a ramp. Ten years later Alexander Mozhaysky's aircraft flew a distance of 30m taking off from a ramp. The pace of advancement was quickening and 1890 saw Clement Alder laying claim to the first powered aircraft capable of taking off from level ground. By 1896 the Australian Lawrence Hargrave had developed a double-wing aircraft or biplane which despite being unsuccessful at the time, paved the way for things to come. In the same year Samuel Langley's unpiloted aircraft 'No. 6' flew a distance of 1.5 km. In 1901 Wilhelm Kress demonstrated the first aircraft to be powered by an internal combustion engine although it was incapable of taking off. 

These early efforts led to the beginnings of an understanding of aerodynamics giving rise to the nascent discipline of Aeronautical Engineering. The brothers Orville and Wilbur Wright are generally acknowledged as the inventors of the first powered aeroplane to carry an individual, having flown a total distance of 114m ten days before Christmas of 1903. Their knowledge of bicycle manufacture had allowed them to fabricate a number of double-wing gliders honing their understanding of aircraft design. It was a watershed moment and, from then on, the development of aircraft and, most importantly, the understanding of the pertinent aspects of flight grew exponentially. Within a decade biplanes were partaking in dogfights over Western France. Despite its success the biplane design had significant efficiency issues and speed limitations. Nonetheless biplanes such as the De Havilland Dragon were being used regularly by fare paying passengers until the mid-1900s.

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1907 saw the invention of the first monoplane by Alberto Santos-Dumont in France, and by the 1930s most aeroplanes had only one pair of wings instead of two. The elegance of the monoplane is probably best depicted by the high-efficiency low-drag aerodynamic design of the Supermarine Spitfire. Improvements in aircraft engine design complemented the advances in aerodynamics, and by the end of WWII, experimental aircraft powered by rockets had flown to the skies, as had the first helicopters. However, the propulsion of modern fixed-wing aircraft lay with a different approach and a technology first developed by Frank Whittle at RAF Cranwell in 1928. Work on the jet engine progressed through the war years so that following the end of hostilities, the jet engine became the dominant aircraft engine technology. Today jet engines are considered to be a very effective means of aircraft propulsion, but require a lot of costly maintenance as their components are stressed to their limits during operation. This, along with their detrimental effects on the environment, has meant the alternatives are being sought actively. So it seems that we may be entering the era of the silent non-polluting 'ionic drive'. Powered flight without motion.
 

Einstein Cartoon - Grey.jpgLittle Einstein’s Corner - Gliding Away 

The first-ever paper aeroplane was made by Leonardo da Vinci over 2000 years ago. We will make one and see how far it glides. For this you will need a sheet of paper and a tape measure. Follow the folding instructions shown. 

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Once finished, hold it above your head and let go to see how far it glides. Using your tape measure, see how far it has flown.
 

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