Chapter 1 The Achievement of Flight Success four flights Thursday morning all against twenty-one mile wind started from level with engine power alone average speed through air thirty-one miles longest 57 seconds inform press home Christmas. Orville Wright telegram sent on 17 December 1903 from the lifesaving station in Kitty Hawk, North Carolina, to his father, Bishop Milton Wright, in Dayton, Ohio. This document announced humankind’s first successful powered flight of a heavier-than-air flying machine. From Cayley’s Triple Paper to Orville Wright’s Telegram Even in a study of NASA’s—and its predecessor agency, the NACA’s—contri- butions to aerodynamic development, one must begin by looking at a fruitful pairing, not of two government agencies but of two remarkable individuals, the Wright brothers. It was the inventive genius of Wilbur and Orville Wright, rather than an institutional imperative, that set the stage for aviation’s astonishing tech- nological progress in the United States and abroad during the twentieth century. Without retracing the path from the earliest concept of the airplane to the pio- neering achievement of the Wrights, readers of this volume will not be able to truly appreciate the formative ideas from which research and development in the field of modern aerodynamics blossomed. The Wrights accomplished what no one before them had the insight to rec- ognize and tackle—they worked out a means of controlling an aircraft aerody- namically by deflecting the wing and tail surfaces themselves, as Wilbur had seen birds do. In this respect, they were far ahead of their predecessors and contem- poraries, including some of the world’s top scientists. The secret of their success was that they learned to fly: before they ever attempted to put an engine on their glider, and thus complete the “invention” of the airplane, they learned how to control a flying machine in the dynamic element of the air. They learned about the use of aerodynamic surfaces to control the airplane in a satisfactory manner and, together with the experience they developed as pilots of their kites and gliders, were able to fly their “powered” plane without difficulty. They were marvelously clear and pioneering thinkers, a rare combination. As such, they deserve a place of distinction at the beginning of any history of modern aerodynamics, especially one published during the centennial of their great achievement. 1 2 Chapter 1: The Achievement of Flight For this first chapter in the first volume of this series, then, there is no more fit- ting destination than the wind-blown sands of Kitty Hawk, North Carolina, where on 17 December 1903, the Wrights made the world’s first successful powered flight of a heavier-than-air craft. The flight of the Wright airplane in 1903 culminated a long, faltering search for basic aerodynamic knowledge, a winding and irregular path that runs far back into the dawn of human experience, back even to our ancestors’ prehistoric fascination with the flight of birds. No doubt, humankind dreamed about flying as soon as humans began dreaming. When civilizations arose, men and women imagined gods in the sky and gave them wings—no mat- ter what ancient civilization one looks at, its gods could fly. The power of flight, denied to mortals, was envisioned as an ability of immortal deities. They lived in the heavens above; they moved across the sky in golden chariots; they soared majestically in and above the clouds. While the materials needed to fabricate a craft resembling a modern hang glider were available thousands of years ago, unquestionably one of the major reasons that mechanical flight did not happen for millennia rested in the basic intuitive misconception that, in order for humans to fly, we needed to imitate birds. But exactly how did birds accomplish flight? Before modern scientific observations with high-speed cameras and, more importantly, before the dawn of a mathematically derived and rational theory of aerodynamics in the early nine- teenth century, naked-eye observation of bird flight fostered a wrongheaded belief in flapping wings. From the wings crafted in ancient Greek mythology by Daedalus and Icarus to the ornithopter designed by Leonardo da Vinci during the Renaissance, the best idea anyone could come up with was to mimic a flap- ping wing structure and adapt it for human use. This path to heavier-than-air flight proved not only ignominiously unsuccessful but also often fatal. Donning makeshift wings of wood, feathers, and cloth, a handful of foolish men in the Middle Ages, flapping away without a whit of aerodynamic understanding, jumped to their deaths from the tops of cathedral towers and castle walls. Not just popular imagination but also esoteric intellectual conceptions of the age mystified flight rather than rationalized it. Various medieval and Renaissance thinkers ascribed the ability of the wing to produce lift to psychic and occult forces possessed by the birds. This view held that for humans to fly required not some understanding and application of natural laws but rather their circumvention through the invocation of magical powers.1 This is not to say that, from ancient times to da Vinci, there was no one who expressed sound aerodynamic ideas. In certain basic respects, aerodynamics 1 Charles H. Gibbs-Smith covers the pre-history of flight in Aviation: An Historical Survey (London: HMSO, 1970). From Cayley’s Triple Paper to Orville Wright’s Telegram 3 began in classical Greece during the fourth century B.C. with the first “scientific” observ- er of nature, the philosopher Aristotle. He developed a theory of motion that a projectile such as an arrow stayed in motion because the air separated in front of the arrow and then rapidly filled in the region behind it. According to this concept, the arrow kept flying because of the constant application of the medium’s force in its wake. Despite being fundamentally wrong (though it was a widely accepted the- ory until Galileo’s time), Aristotle’s “medium theory” represented an attempt to explain the phenomena of flight in rational terms with the help of mental pic- tures of physical operations. This type of visual thinking was a crucial first path- way in the maze leading to mature understanding. With other aerodynamic concepts, Aristotle proved even more insightful. He was the first thinker to elaborate on the notion of a “continuum.” In a radically altered form, this became a basic concept of modern science, the foundation of aerodynamic flow applications today. In his writings, one can also find physical reasoning consistent with a concept of aerodynamic “resistance,” inversely expressed through the appreciation that a body in motion, in Aristotle’s words, “will move indefinitely unless some obstacle comes into collision with it.”2 None of Aristotle’s ideas prompted anyone to consider designing an airplane, however, nor did any of the concepts developed by Archimedes, the greatest engi- neering mind of the Hellenistic world. Archimedes, who developed the mechanical lever, built ingenious catapults, and created a screw device for raising water, is also recognized as founder of the science of fluid statics. But not even Archimedes, the author of the world’s first “Eureka” experience, ever came close to the idea of mechanical flight. It is one thing to say that the brilliant minds of antiquity produced concepts in the raw, like the continuum or hydrostatic pressure that contributed to the development of aerodynamics, but quite another to say that any of them had technological import. If science did not stimulate technology, maybe technology stimulated science? One might think that something like the invention of the kite, which took place in China around 1000 A.D., and which appeared in Europe three centuries later in the form of the windsock, would have provoked aerodynamic thinking. Or that 2 Aristotle expressed most of the major tenets of his natural philosophy in his Treatise on the Heavens (De Caelo), Book I. An excellent English translation of this entire treatise (in two books) was done by Stuart Leggat in 1995. His translation and commentary help the reader to appraise Aristotle’s ideas in relation to the cosmologies of his predecessors. Leggat makes it clear that, while tied to the thinking of his day, Aristotle placed natural philosophy on a new footing, with his use of mathematics-style demonstration and his appeal to observation rather than reliance on what were then more standard forms of argument. John D. Anderson does a good job of interpreting Aristotle’s significance in aerodynamics in A History of Aerodynamics and Its Impact on Flying Machines (Cambridge, England, and New York, NY: Cambridge University Press/Cambridge Aerospace Series, 1997), pp. 14-17. 4 Chapter 1: The Achievement of Flight the understanding of basic aerodynamics improved with the design of windmills, a powerful new machine that migrated into Western Europe from the Near East around the late thirteenth century. But neither seems to have been the case. History records no serious attempt to bridge the gap between the dream of flight, the actual world of invention, and basic scientific understanding of aerodynamic forces until the work of Leonardo da Vinci in the late fifteenth and early sixteenth centuries. Even then nothing came of da Vinci’s thoughts. Leonardo’s precious notebooks, encoded with his curious “mirror-like” reverse handwriting, stayed locked up and unknown in the hands of different private collectors for 300 years. One wonders what might have germinated if da Vinci’s ideas had been pub- lished and widely discussed during the Scientific Revolution of the sixteenth through eighteenth centuries. Certainly no one before da Vinci, or for three cen- turies after him, offered anything close to his astonishing vision of flying machines or considered so many of the principles affecting flight.