The glider designs of George Cayley and Otto Lilienthal were a far cry from the technological sophistication of space flight, and 19th-century designs established basic principles still present in the design of the space shuttle. Mechanization, which started with the Wright brothers, powered flight, giving substance to the age-old human dream of manned flight. War and the onset of commercial flight produced massive improvements in aeronautical design and logistical advances. In the modern era, the very concept of flight has taken mankind into space and inspired plans for manned space travel.
The Arc of Progress: Flight and the Evolution of Aeronautical Technology
In 1810, British inventor George Cayley published a paper that would have a profound influence on human history. Cayley’s paper was a unique hybrid of aeronautics and a practical treatment of the physical mechanics of flight, in which he argued that lift is generated by low pressure on the upper surface of the wing and that curved surfaces are more efficient in producing lift than a flat surface (Sussman, p. 136). Whereas other inventors and scientists had postulated variations on this theme, Cayley argued that lift could be directed and stabilized by adding a steering rudder on the craft’s tail to control motion and a horizontal, movable flap to regulate vertical movement (p. 136). Other subsequent modifications enabled Cayley to construct a workable glider model that flew successfully hundreds of feet above the ground in 1853. It would be decades before the first mechanized flight would prove the genius of Cayley’s concept, but Victorian England witnessed the first application of flight technology.
Wilbur and Orville Wright added a second wing to their early-20th-century design, which gave their new bi-plane added lift. However, it was the addition of a small engine that made possible the force necessary to produce what could truly be called flight (Sussman, p. 137). German inventor Otto Lilienthal’s Practical Experiments for the Development of Human Flight inspired the Wright brothers’ seminal design (Inventor’s Gallery, 2012). Lilienthal proposed a series of conditions conducive to producing flight for his glider design. These conditions, such as starting from a flat surface with a “sailing apparatus very like the outspread pinions of a soaring bird,” made it possible to “fly long distanceswithout taxing one’s strength at all, and this kind of free and safe motion through the air affords greater pleasure than any other kind of sport” (Lilienthal, 1896).
It was Lilienthal’s basic glider concept that the Wright brothers used in their own design. Late-19th century America was home to a strong environment of technological invention, highlighted by developments such as the mechanized “horseless” carriage. Innovation set the Americans apart, and the Wrights were on the cutting edge. Like Lilienthal, they were more concerned with how to sustain flight and with what happened aerodynamically during flight, than with the particulars of getting a craft off the ground (Galison and Roland, p. 325). While the Wrights learned from and drew on the work of Lilienthal and Cayley, it was the brothers’ own unique approach to experimentation that set them apart. They constructed a rudimentary wind tunnel, which produced experimental results they used to develop a propeller and engine that would produce the first mechanized flight in 1903 (p. 325).
Contemporaries of the Wrights improved on their design. Inventor Glenn Curtiss, in particular, was able to design a superior means for lateral motion during flight by improving on the ailerons, the basic design of which is still used in modern airliners today (Galison and Roland, p. 325-26). Less than 20 years after the Wright brothers’ successful experiment at Kitty Hawk, N.C., more than 200 companies formed by inventors like Curtiss and the Wrights were producing their own designs and innovations (p. 327). In Europe, the flight of Roland Garros across the Mediterranean in 1913 was indicative of further improvements on the Wrights’ design and, by the end of World War I, aircraft/flight technology had made another significant leap forward. In France, more than 60,000 highly maneuverable aircraft were produced (Unikoski, 2009). One of the most notable technological advances made during the first world war concerned the propeller, which was changed to face forward rather than backward, a “tractor” design that proved more reliable and produced a higher-performance craft (Unikoski, 2009). In another notable advance, the rotary engine had been succeeded by the more powerful in-line water-cooled engine (2009).
In 1935, California-based Douglas Aircraft successfully tested the DC-3, the sleekest, most powerful commercially produced aircraft yet seen. Douglas engineers gave the DC-3 a wider, rounder fuselage than previous iterations, as well as increased wing area, gross weight and engine power (Spenser, p. 127). Approximately 25 years after the end of World War I, global conflict again produced technological improvements in flight technology. The onset of war in Europe and the Pacific led Douglas to re-purpose the DC-3 design for various war-related purposes, carried out by planes of the U.S. Air Force and the RAF. Douglas produced aircraft that “proved crucial to the war effort. Without them, the United States and its allies could not have staged logistically around the globe” (Spenser, p. 128).
Logistical developments and aircraft redesign during the war helped spur the tremendous growth in commercial airline travel after the war. The construction of airfields during the war provided a ready-made infrastructure, and the construction of four-engine-propeller planes allowed for larger designs capable of carrying more passengers than ever before (p. 128). The demands of commercial competition would place a premium on speed, a problem that required an improvement over the propeller design. During the war, when planes reached 70 percent the speed of sound shock waves formed, which pushed the center of pressure toward the rear of the craft, creating drag and negatively impacting performance (Spenser, p. 129). The advent of wing sweep helped overcome this problem.
Boeing’s modern commercial aircraft utilized new designs incorporating unparalleled degrees of wing sweep - as much as 37.5 degrees - for a faster, more efficient cruise (Sutter and Spenser, p. 93). Other advances on the 747 included 18 tires, which distributed the weight of the plane sufficiently to allow it to utilize the same concrete runways as other, smaller planes (p. 93). The overall design of post-war commercial airliners yielded more versatile, durable and faster aircraft than ever before. Other advances in aeronautics would lead to the development of rocket technology and manned space flight. NASA led the way into a new era of aeronautical exploration.
The Apollo program basically drew on the design of German rockets produced during World War II (Lewis, p. 28). These tremendously powerful versions of a decades-old design evolved into the famous Saturn 5 rocket, a veritable icon of the space program. As has so often been the case in the history of aeronautical technology, obsolescence was the order of the day: “Saturn-Apollo was already obsolete when ‘Eagle’ landed at Tranquility Base July 20, 1969” (p. 28). The space shuttle program produced the next major advance in aeronautical design with the creation of an airplane-based design that could “fly” above the earth’s atmosphere. With dimensions basically matching those of a Boeing 707, the craft was launched from a rocket pad and, at an altitude of about 50 miles, fire its rockets to achieve orbital velocity and eventually rendezvous with the international space station (Lewis, p. 29). Though this successful program has been discontinued, legislation passed in 2010 authorized NASA to work on a manned flight to Mars, a mission that will doubtless produce unprecedented aeronautical technologies.
Galison, P. and Roland, A. (2000). Atmospheric Flight in the 20th Century. New York: Springer Publishing.
Lewis, R.S. “Evolution in NASA: Loss and Cost of Transition.” Bulletin of the Atomic Scientists, April 1970, pp. 28-29.
Lilienthal, O. “Practical Experiments for the Development of Human Flight.” The Aeronautical Annual, 1896, pp. 7-20.
Spenser, J. (2008). The Airplane: How Ideas Gave Us Wings. New York: Harper-Collins.
Sussman, H.L. (2009). Victorian Technology: Invention, Innovation, and the Rise of the Machine. Santa Barbara, CA: ABC-CLIO.
Sutter, J. and Spenser, J. (2007). 747: Creating the World’s First Jumbo Jet and Other
Adventures from a Life in Aviation. New York: Harper Collins.
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