Early Beginnings
Ever since early humans watched birds soar through the air, people have wanted to take to the sky. Many even dreamed of leaving Earth to travel to the stars.
Myths and Legends
Throughout history, people have told stories and legends about
attempts to fly. In ancient Greek myths, Daedalus and his son
Icarus flew with wings made of wax and feathers.
According to the story, Daedalus flew safely, but Icarus flew too close to the sun. When the heat melted the wax, he fell to his death.
According to a Persian legend, King Kaj Kaoos flew around his kingdom in a throne carried by eagles.
A similar legend tells of Alexander the Great flying around his realm in a basket carried by four griffins. A griffin is a mythical creature that is part eagle and part lion.
Steps Toward the Sky
Our steps toward actual flight were not quite as dramatic as the myths. But they were just as fascinating.
The ancient Chinese are believed to have invented the first kites. In 206 BCE, a Chinese general used a kite in his plans to attack an enemy's palace. General Han Hsin flew the kite over the palace and measured the amount of line released.
By doing a little math, he was able to find out the length of tunnel he would need to dig to get inside the palace. Kites later played a key role in the development of airplanes.
In the 1480s, Leonardo da Vinci sketched many drawings of flying
machines. One of these was a design for an ornithopter,
a flying machine with flapping wings. The human body would power
the wings.
Da Vinci also created designs for gliders and for an aerial screw, an ancestor of the helicopter.
Many other people attempted to fulfil the dream of flight. But humans did not make much progress toward that goal until the 19th century. That's when the first lighter-than-air balloons and gliders were invented.
Gliders
In 1804, British scientist and inventor Sir George Cayley built
the first airplane, but it was only a toy. Cayley's invention
was built from a kite fastened to a small stick. A small weight
kept the plane's nose down.
In the 1850s, Cayley built full-size gliders using the same principles as he used with the toy airplane. A young boy was the first to fly one of his gliders.
Cayley was the first to define the three factors required for an aircraft to fly: lift, thrust, and control.
He also wrote an article that outlined his thoughts on the best way to achieve flight. The key, he wrote, was to develop a fixed-wing airplane with a power system to move it forward. A tail would help control the airplane.
German engineer Otto Lilienthal improved on the glider design. By
the end of the century, he had established many principles of
aerodynamics. For example,
he found he could control and steer the glider by shifting his
weight.
First Powered Flight
Two American brothers named Orville and Wilbur Wright spent years building on the designs of Lilienthal and other inventors.
On December 17, 1903, the brothers gathered on a beach near Kitty Hawk, North Carolina. Their gasoline-powered airplane, Flyer I, had cotton-covered wings that were more than 12 metres (40 feet) long.
Flyer I was designed to fly tail-first. Its propellers rotated in opposite directions to push the plane forward. Orville won a coin toss and was the first to attempt to fly Flyer I.
At 10:35 a.m., Flyer I lifted off the ground. It stayed in the
air for 12 seconds and travelled a distance of about 37 metres
(120 feet). It was the first controlled, sustained flight in a
powered airplane.
The Wright brothers knew that the secret of flight was the fact that air exerts pressure. The Swiss scientist Daniel Bernoulli (1700-1782) was the first to recognize this fact.
When a stream of air is separated by a curved surface (or airfoil), the air is forced to travel a different distance on each side of the airfoil (for example, a wing).
The curved top of the wing is a greater distance than the flat
bottom of the wing. Where air travels farther, it moves faster.
This creates an area of low pressure on top of the wing.
On the bottom of the wing, the air moves more slowly. This creates an area of higher pressure on the bottom of the wing. The difference in pressure between the top and bottom of the wing creates an upward force on the wing. This force is called lift.
The Wright brothers had successfully applied Bernoulli's findings. This opened the way for a steady stream of new developments.
Today, airplanes are designed with many airfoils--not just the wings. The fuselage, engine housings, tail assembly, and propellers all act as airfoils.
Other Early Airplanes
Many reliable flying machines were developed in the years after the historic Wright brothers flight. Early airplanes had two or more sets of wings. This helped the planes to gain as much lift as possible.
These airplanes--called biplanes--were gradually replaced by monoplanes. Monoplanes have only one set of wings. This design made airplanes faster and more powerful.
French aviator and inventor Louis BlΘriot flew the world's
first monoplane in 1907. In 1909, he made the first successful
flight across the English Channel in his BlΘriot XI monoplane.
The monoplane is still the design of choice for aircraft today.
By 1912, aviation had spread
around the world. At the beginning of World War I in 1914, airplanes
flew at speeds of 113 to 129 kilometres per hour (70-80 miles per hour)
and at an altitude of 3048 metres (10 000 feet).
By the end of the war in 1918, speeds had increased to 225-241 km/h (140-150 mph), and altitudes had risen to 7315 metres (24 000 feet). These dramatic improvements in just four years were driven by the demands of the war.
New airplanes continued to set distance and speed records after the war.
Pilots competed with each other in air races such as the one that took place
on May 27, 1927.
One competitor, Charles Lindbergh, was a previously unknown barnstormer and mail pilot. The American aviator successfully flew The Spirit of St. Louis on the first non-stop flight across the Atlantic Ocean. He completed his historic flight in 33.5 hours.
Amelia Earhart was one of the most significant figures in aviation. In the 1920s
and 1930s, she achieved a number of "firsts."
The American pilot was the first woman to fly across the Atlantic and the first woman to fly solo across the Atlantic. She opened the first flying school for women. She disappeared in 1937 during her attempt to fly around the world.
Jets
The world entered the jet age on August 27, 1939. On that date, the He-178
monoplane made its first flight. The plane reached the astonishing speed of
700 kilometres per hour (435 miles per hour).
German engineers Ernst Heinkel and Hans Joachim Pabst von Ohain designed the He-178. Their work eventually made the propeller a thing of the past, except for short-distance flights.
The jet engine works on the principle in Newton's Third Law of Motion: for every action there is an equal and opposite reaction. Here is a quick sketch of how the jet engine works:
- air is sucked into the engine
- a compressor pumps the air under pressure into a combustion chamber
- in the combustion chamber, the air is mixed with fuel and ignited
- the resulting gases expand and rush at high speeds out of the exhaust nozzle, driving the plane forward
The jet engine allowed planes to fly at speeds the early aviation pioneers
would have thought impossible.
For example, in 1976, a U.S. spy plane called the SR-71 Blackbird reached 3326 km/h (2193 mph)--more than three times the speed of sound. It also soared up to altitudes of more than 24 kilometres (80 000 feet).
Today, the Blackbird is still considered the world's fastest jet.
With the development of the jet engine, humanity had gained mastery of the sky. But for some, the sky was not the limit. The new dream was space flight.
In 1947, U.S. test pilot Chuck Yeager flew a rocket-powered
X-1 aircraft into the record books.
The plane broke the sound barrier
(about 1192 km/h or 740.7 mph) and showed that rocket-powered flight was a reality.
X-1 landing. NASA video.
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In 1959, another rocket-powered aircraft roared into the sky. During the 1960s,
the X-15 reached maximum speeds of 8000 km/h (4970 mph).
It also soared to altitudes of 108 km (67 mi. or 354 000 ft.). That's so high up that the X-15 had to re-enter Earth's atmosphere!
Developments in jet engines and rocketry played a key role in the space program. For example, the X-15 program explored some of the problems that would be involved in human space flight. Those problems included:
- aerodynamic forces
- heating
- stability and control
- re-entering the atmosphere
- and the effects on the human body at extremely high speeds and altitudes.
Many of the people from the X-15 program went on to work in the Mercury, Gemini, and Apollo programs.