This article is part of the science and technology column at Treehouse. This column aims to distill issues related to science and technology, presenting them in an easy-to-read, digestible format.
The year is 1896. A man lies dying in a clinic in Berlin, Germany, the third vertebra of his neck fractured. He motions for his brother, and gently whispers the words, “Sacrifices must be made!” before slipping away. The dead man is pioneering aviator Otto Lilienthal, mortally wounded after crashing one of his self-designed gliders. Lilienthal’s story is just one example of the innovation and bravery shown by countless inventors in their quest to achieve manned, self-propelled flight.
Beginning in the late 18th century, fledgling aviators experimented with different types of flying craft, including hot air balloons and rotorcraft, to various degrees of success. However, the majority of manned flight would eventually be undertaken by a third category of aircraft, the fixed-wing plane. Early aviators drew inspiration from kites in creating their initial designs, because though a kite is inherently heavier than the wind it glides upon, it stays aloft by generating lift.
Otto Lilienthal himself created a myriad of gliders of various designs, and tested them by leaping from hills, using updrafts to remain airborne. He controlled his gliders solely by shifting his body weight, a technique that inadvertently led to his untimely demise. On that fateful day, his glider pitched downwards, and unable to recover from this position, he plummeted to the ground. Wary of Lilienthal’s fate, American brothers Orville and Wilbur Wright realised that unless a better steering system could be invented and honed, any fixed-wing flight would be a reckless endeavour.
One of the Wright brothers’ early designs, superimposed against the three axes of flight control (image from Nasa Official)
With this in mind, the Wright brothers created a system of three mechanisms to control their aircraft. An array of pulleys and cables enabled them to twist the edges of their gliders’ wings, modifying the amount of lift generated by each, and allowing them to bank in mid-air (known to aviators as roll). A movable, miniaturised wing called an elevator was mounted in front of the pilot, and could be adjusted to change the angle of the craft with respect to the horizontal (known as pitch). Last but not least, a rudder affixed to the rear of the craft enabled side to side turns (known as yaw). This early version of three-axis control gave the brothers confidence to forge ahead with longer and more complex glider flights. In 1903, they added a custom-made gasoline engine, fitted with hand-carved propellers, creating the world’s first powered aeroplane.
When powered flight was in its infancy, nearly every plane built was a biplane. The concept of two wings stacked vertically had its advantages, such as the ability to generate greater amounts of lift, and also provide a higher level of structural integrity. However, the biplane quickly fell out of favour as construction techniques and quality of materials improved. Two wings meant that each wing interfered with the aerodynamic performance of the other, and collectively produced too much drag at high speeds.
For decades, exceeding the speed of sound was viewed as a pipe dream, and conventional propeller driven aircraft simply fell short. Aircraft companies poured millions of dollars into researching new means of propulsion, spawning the jet and rocket engines used in modern day aviation and spaceflight. These burned fuel at much higher rates, generating the vast amounts of power required for supersonic flight. Finally, on October 14, 1947, test pilot Charles ‘Chuck’ Yeager coaxed the rocket-powered Bell X-1 to a top speed of Mach 1.07 (1.07 times the speed of sound).
Diagram illustrating how sound waves are compressed into a sonic boom (image from The Worlds of David Darling)
All aircraft create sound waves in flight that travel in all directions, but as Yeager approached Mach 1 something unprecedented happened; his plane began to catch up with the sound waves in front of it. Compressed together, the multiple waves reinforced each other, creating a shock wave around the X-1; a sonic boom.
Today, modern fighter jets break the sound barrier routinely, reaching speeds of Mach 2 and beyond. The most advanced fighter jet currently in existence is the F-22 Raptor; a fifth-generation combat aircraft that primarily serves as an air superiority fighter. Designed and built by Lockheed Martin with assistance from Boeing, its distinctive contoured design incorporates radar absorbent material, enabling infiltration of hostile airspace without detection. Like most high performance aircraft, the F-22 is a fly-by-wire plane; as pilots adjust the controls, on-board computers relay their input electronically to motors located at various regions of the plane, which steer accordingly. Aspects of flight stability too complex to be controlled by a lone human operator are regulated independently by electronic means instead. This is crucial since the F-22 is engineered to be unstable aerodynamically, in order to improve its manoeuvrability in combat scenarios.
In 2015, 112 years after the Wright brothers’ historic milestone, it is nearly impossible to imagine a world without manned flight. With the establishment of a globe-spanning commercial aviation network, journeys that would take weeks or months by land or sea have been reduced to a matter of hours. Tonnes of cargo are ferried between continents each and every day, and the ever-quickening speed has enabled international trade to flourish. Rocket technology developed in the pursuit of supersonic flight has since carried astronauts into space, and as far as our Moon. One can only guess where the next century of aviation will take us.
Thumbnail image from Wikimedia Commons, header image by Wong Li Ying.
About the Author
Wei Xiang’s two favourite things are books and music. His idea of a good night is one spent reading a thought-provoking novel, with an album playing softly in the background. Of course he has many other interests as well, but those tend to involve, you know, going outside.