Socrates had the right idea. Way back in ancient Greece, he
insisted that: "Man must rise above the Earth—to the top of the
atmosphere and beyond—for only thus will he fully understand the
world in which he lives." Intrepid inventors would spend the next
2000 years making that insistent dream a bold reality. How about the
Italian polymath Leonardo da Vinci, for example, who sketched a
design for a wooden "ornithopter" around 1485, over 400
years before the first powered flight? Or Otto Lillienthal, fragile
wings strapped to his body and flapping furiously, quite convinced he
could fly like a bird—until a fateful date with gravity ended his
experiments, and his life, in 1896.
Photo: Supersonic—faster than sound—flight is the norm for military jets in the 21st century, but it took thousands of years of innovation to get to that stage.
Photo by JT Heineck, with Schlieren data processed by Neal Smith, courtesy of
NASA Ames Research Center.
Scientists weren't always convinced that human flight was a
possibility. William Thomson (Lord Kelvin), one of the most eminent
physicists of the 19th century, confidently asserted that
"Heavier-than-air flying machines are impossible," while another
eminent scientist, Sir George Cayley, thought the opposite: "I am
well convinced that Aerial Navigation will form a most prominent
feature in the progress of civilization." Two science-minded
brothers, Wilbur and Orville Wright, eventually settled the dispite,
proving that Kelvin was absolutely wrong, when they made
the first, stuttering, engine-powered flight in 1903.
Today, we can see that Socrates was a visionary and we're
taking him absolutely at his word with rockets and probes that venture well beyond Earth's
atmosphere into deep space. But in between dreams of the air and the reality of flying,
where exactly did this great adventure—the story of human flight—properly begin?
Let's take a closer look!
Humans first soared to the sky in bold adventures of the
imagination. The wondrous eastern tales of the Thousand and One Nights
(Arabian Nights), for example, feature a magic carpet, while another ancient Persian
epic, the tale of Kay Kāvus, includes a flying throne carried by
specially trained eagles. Something like 5000 years ago, an ancient
Sumerian shepherd-king named
Etana is reputed to have hitched a ride
to heaven on the back of an eagle. Several thousand years later,
while Socrates was busy imploring people to take to the skies,
fellow ancient Greeks were all too aware of the perils, real or
metaphorical, of over-reaching themselves: the famous Greek legend
tells how Icarus fell to Earth after flying too close to the Sun with
hasty wings made of feathers and wax. The Greeks also had a flying
horse called Pegasus, while the Romans, following in their ancient
footsteps, had Mercury, their own winged messenger from the heavens.
Photo: A statue of the winged messenger Mercury at Saltram House in Devon.
Look closely and you'll see the wings under his hat!
Stories like these, which we're still recycling to this day,
must have played an inspiring part in the first real attempts to take
to the sky along, of course, with practical observations of birds,
insects, and other flying creatures. No-one knows who made the very
first human flight—or when—but one strong candidate is
Firnas (810–897CE), an Andalusian version of Leonardo da Vinci, who
jumped from a tower in Cordoba (now Spain) around 850 with flapping
wings strapped to his body and reputedly flew quite some distance.
Over in Malmesbury, England about a century later, a young monk named
Eilmer attempted a similar flight, proudly commemorated in a piece of
stained glass in the town's abbey. Using a pair of crude homemade
wings, he reputedly glided a distance of about 200m (650ft) from the
Abbey tower before crash landing and breaking both legs, rendering
him lame for the rest of his life.
Photo: A boy sets off on a flying carpet in adventures of the imagination.
Photographs in Carol M. Highsmith's America Project in the Carol M. Highsmith Archive,
Library of Congress, Prints and Photographs Division.
There's more than one way to fly—and the first real flights
might be better described as "floats," since they involved
buoyant (floating) balloons rather than winged aircraft. The science
of floating, as we understand it today, was clearly understood by
Archimedes (287–212BCE) around 2200 years ago.
Famously, he figured out how objects displace (push aside) their own
weight of fluid, which is the first step toward understanding
why ships can float on the sea. Though Archimedes floated
these thoughts c.200BCE, the first balloonists are thought to have
taken to the air long before then. Some believe that the Nazca people
of southern Peru built balloons hundreds of years earlier, perhaps
c.500BCE, from which they planned the famous, vast, incredible
artworks in their dusty desert landscape (popularly known as Nazca
Lines) that are still visible from the air to this day (though this
explanation is controversial and disputed).
Photo: Hot-air balloons fly by floating.
It takes a flight of insight to understand that the same science
floating boats on the sea allows balloons to rise and float in
the air. The person who figured this out was English polymath
(c.1214–1294); taking Archimedes' ideas a step further, he
understood that air pressure could support a balloon in the same way
that water pressure supports a ship. All very well in theory, but how
could you achieve it in practice? Modern
balloons have hot air inside
them that's less dense (lighter) than the air around them, so they
feel a force called lift that makes them rise into the sky. The basic
science—hot air is less dense than cool air—was first properly
worked out by a brilliant 17th-century chemist named
(1627–1691), but people had an intuitive grasp of the idea long
before then. Over 2000 years ago,
Chinese children are believed to have played with toy flying "machines" made from eggshells with
burning twigs inside them. As the twigs burn, they heat up the air
inside, making the shell into a miniature hot-air "balloon" that (supposedly, if it's
not too heavy) rises into the sky. Sweet wrappers (Amaretto papers) that fly into the air when
they burn look like mini hot-air balloons but work on different principle
(the burning paper creates an invisible draft of rising hot air that eventually sucks the paper up with it).
Though the theory and practice of using hot air to make lift seems
to have been known for thousands of years, it wasn't until 1783
that the first proper hot air balloon was created, by French
brothers J. Étienne and Joseph M. Montgolfier (1745–1799 and 1740–1810). With an "envelope" (gas-containing bag)
fashioned out of cloth and paper, blown high by a straw and wood fire
burning beneath, their pioneering aircraft achieved an amazing height of 900m
(3000ft). Later that year, they safely sent a sheep, rooster, and
duck into the air, before Étienne Montgolfier became the first human
balloonist (albeit safely tethered to Earth by rope) shortly afterward.
A few weeks later, the first free-floating balloon flight
carried Jean-François Pilàtre de Rozier and Marquis François
Laurent le Vieux d'Arlandes high over Paris in a Montgolfier balloon.
Illustration: A later flight by the Montgolfier brothers and their passengers over Lyon, France, on January 19, 1784. Hand-colored etching: Enaut et Rapilly, rüe St. Jacques à la ville de Coutances, 1784,
courtesy of US Library of Congress.
Hot air balloons evolved into steerable, engine-powered airships
called dirigibles, which were pioneered by another Frenchman,
Henri Giffard (1825–1882), in the first part of the 19th century. By the
end of the 1900s, they'd evolved once more, into huge passenger-carrying balloons called
named for German army officer Count Ferdinand Graf von Zeppelin (1838–1917). Unlike the
Montgolfier's balloon (and modern hot-air balloons), airships like
this were rigid-framed rubber balloons containing a number of individual
cells filled with hydrogen, a very light gas. In the early decades of
the 20th century, when wing-powered airplanes were still a very new
thing, airships seemed to be the stately future of intercontinental
travel. But hydrogen has a huge drawback—it's highly
flammable—and a series of spectacular disasters soon put paid to
that idea. The worst of these happened in May 1937 when an enormous
German airship called the
Hindenberg (about 245m or 800ft long)
as it landed in New Jersey killing 36 people.
Maybe there were better ways to fly?
Finding our wings
Airships and balloons are vast, clumsy, and cumbersome things:
they need a huge volume of lighter-than-air gas to make enough lift
to overcome their weight. The giant, fateful Hindenberg, for example,
needed something like 200,000 cubic meters (7 million cubic feet) of
hydrogen, while even a more modest Zeppelin needed about 14,000 cubic
meters (500,000 cubic feet). Modern airplanes carry much bigger loads
than these airships without any help from floating gas bags at
all—and they do it using wings. Broadly speaking, the larger the
plane (or the heavier the load it has to carry) the bigger the wings
Exactly how wings help a plane to fly is quite a complex thing
(you'll find it explained in detail in my article about how planes
fly). A plane doesn't necessarily need an engine, but it does need
wings: it's the wings that make the upward lift when the engines
push the plane forward through the air. If you make a plane go
forward without an engine, its wings will still generate lift. That's
the idea behind gliders, which are simply planes without engines. As
we've seen already, one of the first pioneering historic flights,
by Eilmer the Monk in Malmesbury, was essentially a glider flight by
a man with wings strapped to his body.
Gliders—and the science of flight—made huge strides forward in
the 18th and 19th centuries thanks to a brilliant English aristocrat
named Sir George Cayley
(1773–1857). Unlike so-called "birdmen"
aviators, who tried to fly by flapping wings attached to their
bodies, Cayley concentrated most of his efforts on the design of fixed-wing aircraft and figured
out how to optimize the wings to maximize lift. He made his first model
glider in 1804 and spent the rest of his life refining the design
until, in 1853, he was ready to launch a full-sized glider with a
human inside it.
Photo: "Birdman" Otto Lilienthal flying one of his gliders in 1895,
the year before his death. Photograph attributed to the Wright brothers (a glass negative from the papers of Wilbur and Orville Wright) courtesy of US Library of Congress.
Cayley's work took flight in two different
directions, practical and theoretical. From the practical side, it
helped to inspire glider makers like
Jean-Marie Le Bris (1817–1872) and
Otto Lilienthal (1848–1896), who made 2000 daring glider flights before
finally crash-landing and killing himself in 1896. Cayley's work
also marked the real beginnings of the science of aerodynamics, later
extended by Lilienthal's experiments with airfoil design and
20th-century pioneers such as
Ernst Mach (1838–1916, who researched
supersonic flight, and for whom Mach numbers are named)
and Frederick Lanchester (1868–1946, another
pioneer of modern airfoil theory). Cayley was the first person to figure out that a plane moves through the air in
a balance of four forces: thrust (moving it forward), drag (air
resistance, pulling it back), lift (the upward force on the wings),
and weight (the force of gravity pulling the plane back down).
Illustration: Getting in a flap: One of Sir George Cayley's human-powered flying machines, c.1853.
Courtesy of US Library of Congress.
People still fly gliders to this day, but they're typically just
small, one- or two-person craft that take great skill to pilot. Though it's
just about possible to imagine a glider that could carry more, no
glider could ever do what modern jet planes do—ferrying hundreds of
people at high speed over deserts, mountains, and oceans, day after day,
year in and year out. For that kind of dependable, steady
flight, you need more than just a plane with wings; you need a plane
with powerful engines.
“I can state flatly that heavier than air flying machines are
impossible... I have not the smallest molecule of faith in aerial
navigation other than ballooning, or of the expectation of good
results from any of the trials we heard of.”
Lord Kelvin, 1895/1896
Where would those engines come from? Since the early 18th century,
most of the world's mechanical power had come from coal-powered
steam engines, the first practical example of which was built by
Thomas Newcomen, in England, in 1712. Steam engines were huge dirty
beasts, originally much too big and bulky even to drive things like
railroad engines, so there was no prospect of using them to power a
plane. Even so, that tantalising possibility opened up with the
development of smaller, lighter, high-pressure railroad steam
engines, by such people as
Richard Trevithick (1773–1833) in Britain and
Oliver Evans (1773–1833) in the United States.
Ultimately, a number of engineers believed it was perfectly worthwhile to experiment with putting steam
engines in planes. It seems a remarkable idea now—using a
heavy, coal-powered engine to lift itself off the ground—but
there was still no serious, credible alternative to steam at the
time. That's why a number of intrepid inventors in different parts
of the world seriously experimented with steam airplanes, including
Englishman William Henson,
Frenchman Clément Ader, and Americans
Samuel P. Langley,
Hiram Maxim (inventor of the automatic machine gun), and
None of these attempts got beyond models and
prototypes and, though several made promising flights, none led to
the development of a practical, steam-powered airplane.
Illustration: William Henson's
Aerial Steam Carriage, optimistically sketched making a bold voyage
over the Thames River in London c.1843. Although Henson and his partner John Stringfellow were granted a patent
in 1842, in reality, even a model of this stupendous steam plane never got off the ground.
Courtesy of US Library of Congress.
The Wright stuff
Photo: A statue of Orville Wright at the Wright Brothers National Memorial in Kill Devil Hills, North Carolina. Credit: Photographs in Carol M. Highsmith's America Project in the Carol M. Highsmith Archive,
Library of Congress, Prints and Photographs Division.
At the end of the 19th century, gliders were still the
state-of-the-art when it came to flying machines, but two talented
brothers from Dayton, Ohio soon changed that.
Wilbur and Orville Wright
were bicycle makers who were also familiar with a new
development in powered transportation. Though steam engines still
dominated factories and transportation, a very different kind of
engine had recently emerged, which could be powered by
a relatively clean liquid: gasoline. The first practical engine of this kind was developed in
1867 by a German engineer named Nikolaus August Otto (1832–1891),
and a similar engine was used to drive the first gasoline-powered car in 1885
by another German, Karl Benz (1832–1891). Engines like these were
smaller, lighter, and much cleaner than steam engines—and that
opened up the possibility of using them to power a plane.
The Wright brothers' stroke of genius was to connect two
different strands of invention: the glider, which had been driven
forward by people such as Cayley, Lilienthal, and the American
Octave Chanute (1832–1910), and the gas-powered automobile engine, shaped
by Otto and Benz. When the Wrights put a small (9-kilowatt or 12
horsepower) gasoline engine onto a glider, the result was the world's
first self-propelled, engine-powered airplane, the Flyer. It
would have been perfectly possible for the Wrights to arrive at a
practical airplane through nothing more than trial-and-error—that's
how many things were invented in centuries gone by—but they
actually took a much more scientific approach. As their notebooks and papers clearly reveal, they carried out meticulous experiments into all
kinds of different wing shapes and propeller designs, so
their approach to invention was much more modern and scientific than most people realize.
Artwork: The "Flying Machine" patented by the Wright brothers in 1906 was essentially a biplane glider. It's a biplane because it has two parallel main wings (blue); it's also what's called a bicanard, because it has another wing (red) in front of the main wings. The all-important engine (indicated by the yellow spot) and propellers (orange circles at the back) are not shown in this drawing. From US Patent 821393: Flying Machine, by Orville and Wilbur Wright, filed March 23, 1903, granted May 22, 1906, courtesy of US Patent and Trademark Office..
Once the Wrights had made the all-important breakthrough, other
engineers developed their ideas, while brave aviators tried to push
technology even further by making amazing, long-distance flights. The
many pioneers included Frenchman
Louis Blériot, who crossed the 40km
(25 mile) English Channel in 1909; American
Curtiss, who won $10,000 flying from New York City to Albany the following year;
Calbraith Rodgers, who became the first person fly across the United
States, from New York to California (albeit in many separate hops
taking a total of 84 days) in 1911;
John Alcock and Arthur Brown, who made the first Atlantic crossing in 16 hours 12 minutes in 1919;
Charles Lindbergh, who flew nonstop from New York to Paris in 1927; and
Amelia Earhart, who became the first woman to cross the Pacific in 1932.
Photo: Bronze statues recreate the Wright brothers' first powered flight in North Carolina.
Credit: Photographs in Carol M. Highsmith's America Project in the Carol M. Highsmith Archive,
Library of Congress, Prints and Photographs Division.
The coming of the jet
All these planes had one thing in common—they were powered by
propeller engines—and, though the planes of the 1930s flew faster
and further than the Wright's 1903 Flyer, they still used
essentially the same technology. But propellers, originally powered
by piston-powered car engines, could spin round only so quickly
before tearing themselves to pieces, and engineers soon realized that
there was a practical limit to how fast an ordinary engine could go,
which set an upper limit to how fast a plane could fly. That didn't
matter while planes were carrying only one or two people very short
distances, but it became increasingly important with the development
of military planes that needed to "outfly" and outmaneuver their
enemies, and large passenger planes that could carry numbers of people
from one side of the world to the other.
Photo: Jet planes fire forward by blasting hot exhaust gas backward.
Photo by William Banton courtesy of US Air Force, published on
So engineers started to ask themselves if it was possible to power
planes another way. A glimpse of the future came in 1910, just a few
years after the Wrights' pioneering flight, when a Frenchman named
Henri-Marie Coandă (1885–1972) flew the first jet-powered airplane,
though it was propelled by a huge fan rather than the burning gas
used in later planes. It wasn't until the 1930s that modern jet
engines properly appeared, thanks to the dogfight rivalry between
Englishman Frank Whittle (1907–1996) and his German counterpart,
Hans Pabst von Ohain (1911–1998). Though Whittle made the first jet engine in 1928, Ohain built the first jet plane, the Heinkel He-178,
in 1939. Whittle and Ohain are popularly remembered as the jet
engine's pioneers, though others were crucial to its development,
including British engineer
Alan Griffith (1893–1963), who outlined
the theory of jet engines in 1926.
The arrival of the jet engine was almost as big a breakthrough as
the Wright's first pioneering flight. Whittle's original jet
engine was a design known as a turbojet (in which cold air streaming
into the front burns with fuel to make hot exhaust blowing out of the
back that speeds the plane forward). Other types of jets soon appeared in the
form of turboprops (jet engines with propellers at the front),
turbofans (giant jet engines used on modern airliners), and a variety
of other designs (explored in much more detail in my article on jet engines).
Engines like this ushered in a whole new era of fast,
jet-powered military and passenger planes. And the arrival of jet
airliners like the DeHavilland Comet (in 1952), the Sud Aviation
Caravelle (1955), the Lockheed Electra (a popular turboprop from
1957), the Boeing 707 (a four-engined jet launched in 1958), the
Douglas DC-8 (1958), the Convair 880 and 990 (1959), powered the age
of affordable intercontinental travel that we all now take for
granted. With its four huge "bypass" turbofan jet engines, the
iconic example, the
Boeing 747 "Jumbo" jet, can carry 300–500 passengers at speeds of 885km/h (550mph) across whole continents. But
people still dreamed of going faster.
Photo: Jumbo Jet: A full-sized Boeing 747 on the roof of the Evergeen Museum
at McMinnville, Oregon. Courtesy of Photographs in the Carol M. Highsmith Archive,
Library of Congress, Prints and Photographs Division.
Before long, a typical transatlantic trip across the Atlantic took
as little as six hours. That was pretty amazing if you compared it to
Charles Lindbergh's 33.5-hour transatlantic flight in 1927, but
still not fast enough for many people. Could planes fly any faster?
Just how fast could they go? One major landmark engineers identified
was going faster than the speed of sound, which is very roughly 1000
km/h (660 mph—though it varies with altitude). In the early decades
of the 20th century, no-one knew if this was remotely possible: would
a plane flying that fast simply rip itself to pieces? In the 1940s, some of the world's best aero engineers
set themselves the challenge of finding out by developing a rocket-powered plane called the X-1.
Strapped in its cockpit in
October 1947, Major Charles E. ("Chuck") Yeager (1923–)
became the first person to fly faster than sound at a speed of 1066 km/h (662
mph). Today, military jets routinely fly much faster.
(The world's fastest jet plane, the Lockheed SR-71B "Blackbird,"
has a top speed of Mach 3, three times faster than the speed of sound,
or about 3185 km/h (1979 mph).
Once the technical problems of supersonic (faster-than-sound)
sound had been conquered, the question was whether conventonal
passenger planes could ever fly that fast. In the 1960s and 1970s, engineers in
the Soviet Union (Russia and its nearby, politically aligned states)
and Europe (specifically Britain and France) decided to built
supersonic passenger jets. The Soviet attempt, the Tupolev TU-144,
carried cargo and passengers from the mid-1970s to the early 1980s,
when it was finally withdrawn after proving too expensive and
unreliable. Concorde, the much-more-famous Anglo-French equivalent,
was a symbol of glamous transatlantic travel from the first flights
in 1976 to a terrible crash in Paris in July 2000 that effectively brought its
quarter-century history to a tragic, premature end. Though only 16
Concorde were ever built, and lost a reputed $1 billion over their
lifetime, they still hold the record for transatlantic passenger
flights, flying from London, England to New York in about 3½ hours,
compared to about 8½ hours for a conventional jet flight.
Concorde's "cruising" speed was 2160 km/h (1350mph), roughly Mach 2 (twice the
speed of sound).
Flying by spinning
You can fly by floating straight up or by forcing air across a
pair of wings. But there's another way to fly too that combines the
best of both worlds: by taking off or landing vertically in a
helicopter, which uses a kind of spinning central wing called a
rotor. Helicopters were conceived in ancient China: a toy from the
ancient East used a clever arrangement of spinning feathers to breeze
itself up into the air, not unlike a modern chopper. Although most
people think Leonardo da Vinci invented the helicopter, the
rotating flying machine he sketched around 1489 never got off the drawing
board. And though Sir George Cayley tried to apply some of his
pioneering aerodynamic ideas to the problem of vertical takeoff, he
too never managed to lift a helicopter off the ground.
Photo: A prototype helicopter made by Henry Berliner some time between 1920 and 1925.
You can see it has a propeller for forward flight and two counter-rotating rotors for hovering.
Photo from the George Grantham Bain Collection courtesy of US Library of Congress.
Helicopters as we know them today first appeared in the 1920s and 1930s. The
pioneers were Frenchman Louis Breguet (1880–1955), who launched his simple Gyroplane in 1935; German Dr Heinrich Focke (1890–1979),
whose Focke-Wulf FA61 helicopter could fly to altitudes of about 2400m
(8000ft) and stay there for about an hour and a half;
Spanish engineer Juan de la Cierva (1895–1936), who invented the Autogyro—half helicopter
and half plane—in 1920; and American
Henry Berliner (1895–1970), who experimented with winged "gyrocopter" airplanes that had propellers and spinning rotors.
But the real father of practical modern helicopters was surely brilliant Russian aerospace engineer
Igor Sikorsky (1889–1972). As a boy, he'd built
himself a toy helicopter that was powered by rubber bands, but it
took him several more decades to turn this simple childhood dream
into a practical flying machine, the VS-300. It set the shape and
style of modern copters with a large overhead rotor (for taking off,
hovering, and landing) and a small spinning tail rotor (to stop the
body of the helicopter counter-rotating). Though modern helicopters
look like massive propellers mounted on cabinets, they're actually
powered by one or two jet engines (known as turboshafts), which use
complex gear mechanisms to power both rotors.
The story of flight didn't stop with the invention of the jet
engine. Rocket engines, which look similar to jet engines but work in
a rather different way, blasted the story off in a whole new
direction—up and out and far into space. (That's a whole
different tale, explored more in my article on space rockets.) In
the 1970s, engineers fused the idea of a plane flying with
wings and a rocket engine that could burn in space to make the Space
Shuttle, the first reusable plane that could roar into space
and then glide back to Earth again.
Today, the quest is to build planes that can ferry tourists up to space and back—a
milestone that seems likely to be achieved in the next few decades.
Meanwhile, back on Earth, though there's no longer any particular
need to make passenger planes that much bigger or faster, there are
other pressing problems to solve, notably environmental ones. Can we
make planes that are quieter, more energy efficient, and less
polluting? Already, ingenious engineers are experimenting with solar
planes and battery powered electric craft that use electric motors
and propellers instead of roaring, polluting jet engines.
Where will flight take us tomorrow? How will this story end? In exactly the same
way it began, with a bold determination to "rise above the Earth—to
the top of the atmosphere and beyond" so we can "fully understand
the world" in which we live. Watch this space!
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