Category FLIGHT and M ОТІOIM

The concept of jet power has been around for thousands of years. In the first century c. e., Hero (also known as Heron) of Alexandria, Egypt, invented a jet-powered device called the aeolipile. It was a hollow metal ball sup­ported on a frame. Steam inside the ball escaped through two bent pipes. The jets of steam rushing out of the pipes made the ball spin.

Today’s jet engines produce power by a similar, simple process of heating gas. Fuel burned inside an engine combines with oxygen from the air to produce hot gas. As the gas heats up, it expands so much and so fast that it blasts out of the engine as a high-speed jet.

Jet engines were originally developed to produce faster fighter planes. Since then, the use of jet power has spread to airliners and helicopters and further afield-to ships, record-breaking cars, and other uses.

What Is Jet Power?

Jet power is a kind of power that follows Isaac Newton’s third law of motion, which says: “To every action, there is an equal and opposite reaction.” The action and reaction are equal and oppo­site forces. The jet of gas rushing out of a jet engine pushes against the engine, and the engine pushes back against the gas. They push each other in opposite directions.

The easiest way to see this in action is to blow up a balloon and then let it

The animal world used jet power long before humans discovered it. Squid, octopus, and cuttlefish are among marine creatures that use jet propulsion. They suck in water and then blow it out in a fast jet to pro­pel themselves through the water. Squid have been recorded jetting through the water at up to 25 miles per hour (40 kilometers per hour). The scallop shellfish uses jet propul­sion to escape from danger. It quick­ly snaps the two halves of its shell together, squirting out water in the process. The squirt produces a jet, enabling the scallop to scoot out of harm’s way.

Turbine Engines

Jet thrust is only one way of using jet power. The turbofans that power jet planes use a jet of gas from the engine to spin a large fan at the front of each engine. Turboprop engines use a jet to spin a propeller. The engines that power most helicopters today use the jet of gas from their engines to turn the aircraft’s rotors. All of these engines are known as gas turbines, or turbine engines.

In the 1930s and 1940s, turbine engines for aircraft were developed by two men working separately: Frank Whittle in England and Hans von Ohain in Germany. The introduction of jet power produced a sudden leap in aircraft speeds. The first jet fighters built in the 1940s were 100 to 200 miles per hour (160-320 kilometers per hour) faster than piston-engine fighters of the period. They triggered a race among nations to develop faster and faster mil­itary jet planes.

О A large jet engine is opened up for maintenance.

Newton’s three laws of motion are the most well known, but there are other such laws. Newton’s work on forces, motion, and gravity built on earlier work by German mathematician Johannes Kepler (1571-1630). Kepler studied the way that the planets move. Using observations of the planets made by Danish astronomer Tycho Brahe (1546-1601), Kepler produced three laws of motion for planets.

Kepler’s first law says the shape of a planet’s orbit is a squashed circle, or ellipse. The second law says a line between a star and a planet sweeps out equal areas in equal periods of time. A planet, therefore, travels through space faster when it is closer to a star and more slowly when it is farther away from the star. Kepler’s third law describes the link between the time it takes a planet to go around a star and the length of its orbit.

Newton’s laws of motion and gravi­tation provided a scientific explanation for Kepler’s laws. Kepler’s laws describe the motion of planets, but they apply equally to the motion of modern-day satellites and manned spacecraft travel­ing around planets and moons.

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SEE ALSO:

• Force • Gravity • Lift and Drag

• Newton, Isaac • Thrust • Weight

and Mass

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At first, homebuilt microlights had a poor reputation for safety; they were flimsy, and pilots flew with­out any proper training. Safety has improved. Some countries now require microlight pilots to have a license or certificate, and the air­craft themselves have to be certified as airworthy. France and the United States have the fewest regulations on microlight flying; Germany, Italy, and the United Kingdom are the strictest nations.

In the United States, it is possi­ble to fly an ultralight without holding a pilot’s license, although sensible beginners learn how to fly from an experienced pilot. A sport pilot’s certificate is required to fly light-sport aircraft. A light-sport aircraft has a maximum weight of 1,320 pounds (600 kilograms) and a maximum speed of 138 miles per hour (222 kilometers per hour).

An ultralight pilot is allowed to do simple maintenance tasks at home, just as a person might work on a car or bicycle. Regulations restrict ultralight flying in populat­ed areas, and pilots are not sup­posed to fly in bad weather or at night. Many experienced airplane

pilots have become microlight enthusi­asts, and this has helped raise the stan­dards of piloting.

umans have long been fascin­ated with flight, as ancient myths and legends reveal. Some stories were about flying gods, while others told of magical winged creatures. Some of the most interesting tales told of bold humans who attempted to fly.

Gods of the Air

It is not very surprising that ancient humans-bound to Earth-would believe their gods had the ability to fly. This ability underscored the difference between the human and the divine.

Some gods simply moved through the air in unexplained ways. Others are shown with wings. The ancient Egyptian god Horus had the body-or sometimes just the head-of a falcon. Garuda, a god of ancient India, had the body and arms of a human and the wings, head, and claws of an eagle. The Zoroastrian religion of ancient Persia showed its chief god, Ahura Mazda, with large wings-in some depictions, in fact, the god is just a circle flanked by huge wings. The Greek gods Eros and Nike were also shown with wings.

While many ancient gods could fly, this ability is generally not a central fea­ture of myths about them. An exception is Helios, the Greek god of the Sun. He rode a chariot through the sky each day, carrying the Sun on its daily journey.

One interesting Greek myth tells of the dangers of misusing the power to fly, even for the gods. One day, Phaeton, the

son of Helios, drove his father’s golden chariot on his own. The young god did not have the strength or experience of his father, however, and the horses pulling the chariot went out of control. Zeus, king of the gods, knew that Earth would be scorched if this continued. He threw a thunderbolt to stop the runaway chariot. The horses returned to their nor­mal course, saving humankind, but the young god was killed.

There are other ancient mythologies that include flying vehicles used by the gods. Baal, the god of the Canaanite people who lived in what is now Israel,

rode a chariot of clouds. Indian myths are full of stories about flying vehicles called vimanas, which the Hindu gods often used in battle.

ight Witches were a group of women combat pilots in the Soviet Union who fought in World War II (1939-1945). They flew at night, and they were so deadly that the Germans gave them the nickname of “Night Witches.”

Women in Combat

The Soviet Union was the only Allied nation in World War II to use women pilots in combat. Women flew military aircraft in the United States, Canada, and the United Kingdom, but only on transport or delivery flights. Such mis­sions could be difficult and often haz­ardous, but there was a low risk of encountering enemy aircraft.

During World War II, Soviet armed forces fought a desperate battle against large German armies following the German invasion of Russia in the sum­mer of 1941. The Soviets were desper­ately short of planes and pilots. In the

Communist Soviet Union, women drove farm tractors and trucks alongside men, so-Soviet generals reasoned-why not train them to fly combat planes?

Three regiments of female combat pilots were formed in the Soviet Union in 1942. The Night Witches belonged to the 588th Night Bomber Regiment. The pilots, mechanics, and weapons person­nel in this unit were all women.

The Night Witches flew old – fashioned Polikarpov Po-2 biplanes, really only suitable as training airplanes. These wooden and fabric planes had a top speed of only 94 miles per hour (150 kilometers per hour). The Po-2 biplanes had such weak engines that they could carry only two bombs. Possibly female pilots were given such old planes because the military did not have great concerns for their safety, but the Night Witches developed some tricks that surprised everyone.

Some aircraft do not have ailerons or elevators because they do not have nor­mal wings and tail. Flying wing aircraft have no tail at all. These aircraft use a different type of control surface called an elevon, which is a tilting part at the back of the wing. Elevons combine the jobs of the ailerons and the elevators. If the elevons tilt up or down together, they work like elevators to raise or lower a plane’s nose. If they work in opposite
directions, one up and one down, they work like ailerons and make a plane roll.

Most airplanes have two small wing­like parts, one on each side of the tailfin. They are called tailplanes, or horizontal stabilizers. An elevator at the back of each stabilizer tilts up or down to con­trol pitch. Some planes have a different type of tailplane. The whole tailplane tilts instead of just the elevator. It does the job of the stabilizer and elevator together and is therefore sometimes called a stabilator. Other names for this part are all-moving tailplane or all­flying tailplane.

In some fighter planes, the pitch is controlled by small, tilting winglets on the nose known as canards.

Date of birth: May 26, 1951.

Place of birth: Los Angeles, California. Major contribution: First American woman to reach space.

Awards: Induction into National Women’s Hall of Fame and the Astronaut Hall of Fame; Jefferson Award for Public Service; Von Braun Award; Lindbergh Eagle; NCAA’s Theodore Roosevelt Award; NASA Space Flight Medal (twice).

fter graduating from high school in Los Angeles, California, Sally Ride went on to attend Stanford University in California. She graduated in 1973 with degrees in physics and English. Deciding to focus on astro­physics, Ride earned her master’s degree in 1975 and her doctorate in 1978, both from Stanford.

In January 1978, Ride was one of six women chosen by NASA for astronaut training. Her first chance to fly in space came in 1983. On June 18, she joined four other astronauts on STS-7 aboard the Space Shuttle Challenger. Ride’s main task was to work the Space Shuttle’s robot arm. This mission was the first to use the robot arm to deploy and to retrieve a satellite. STS-7 flew for six days before returning to Earth.

Ride’s second mission, STS 41-G, took off on October 5, 1984. Once again she flew in the Space Shuttle Challenger. This mission lasted eight days, and Ride worked the robot arm to deploy a satel­lite. The seven-member crew also carried

out experiments. This flight made Ride the first American woman to fly twice in space. Fellow astronaut Kathryn Sullivan became the first American woman to walk in space.

Ride was assigned a further Space Shuttle flight in 1985 and began prepar­ing for a launch the next year. That mis­sion was canceled when, in January 1986, Challenger exploded shortly after takeoff. The Challenger disaster caused NASA to ban further Space Shuttle flights until the cause of the explosion could be determined. Ride was chosen to sit on the commission that investigated the accident.

After that work was complete, she transferred to NASA headquarters in Washington, D. C., where she worked on long-range planning for the agency. Her Ride Report, issued in 1987, recommend­ed using the technology of space explo­ration to study conditions on Earth. This Mission to Planet Earth, as it was called, has been undertaken by NASA. Much of the research focused on the issue of cli­mate change. Another Ride recommen­dation was to begin planning for a mission to Mars. At the time, NASA did not pursue this plan, but instead focused its work on the International Space Station.

In 1987, Ride left NASA to accept a position at the Stanford University Center for International Security and Arms Control. Two years later, she joined the faculty of the University of California at San Diego, where she taught and carried out research in physics. For many years, Ride also directed the California Space Science Institute, although she left that post to focus on research, teaching, and her many other activities.

Over the next twenty years, Ride served on several government commit­tees involved with space and technolo­gy. When the Shuttle Columbia exploded in 2003, NASA launched a new investi­gation. As with the Challenger incident, Ride was a member of the commission studying that accident.

Ride also dedicated herself to pro­moting interest in science and space exploration among young people, espe­cially girls. She wrote several children’s books on space and took an active role in other efforts to build the popularity of space exploration. In 2001, she founded her own company, Sally Ride Science, to motivate girls and young women to pursue careers in science, math, and technology.

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SEE ALSO:

• Astronaut • Challenger and

Columbia • NASA • Space Shuttle

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shock wave in air is a sudden, huge rise in air pressure. Shock waves affect the flight of high­speed aircraft and spacecraft through the atmosphere.

Everyone who has heard thunder has experienced the effect of shock waves. A flash of lightning instantly heats the air to as much as 60,000°F (33,320°C). When air is heated, it expands. When it is heated to such a high temperature so quickly, air expands explosively and forms a shock wave. The shock wave rushes away from the lightning faster than the speed of sound. Within a few feet, it has slowed down and become an ordinary sound wave, which we hear as
thunder. Similarly, the sharp crack of a whip is produced when the tip of the whip goes faster than the speed of sound and sets off a shock wave.

Aircraft

When an aircraft flies through the air, it pushes the air in front of it out of its way, which causes disturbances in the air. Pressure waves travel away in all directions. The fastest they can move is the speed of sound. When the aircraft goes faster than the speed of sound, the pressure waves ahead of it cannot escape fast enough. They pile up togeth­er in front of the aircraft and produce a sudden jump in pressure-a shock wave. This shockwave spreads out from the aircraft’s nose in the same way that a wave forms in front of a ship’s bow. Another shock wave spreads out from the aircraft’s tail as air rushes into the hole left behind by the plane, like the wake that trails behind a ship. Other parts of a plane, such as the wings and

cockpit, produce more shock waves, but the nose and tail shock waves are the biggest.

he history of flight is a history of progress for humanity. Today, using air and space, we commu­nicate and travel, defend ourselves against various threats, and explore the world around us and the vastness of space beyond. Pessimists can point to alarming increases in the destructive capacity of humans due to atomically armed bombers and intercontinental ballistic missiles. Optimists-such as myself—can point to the tremendous benefits that air and space travel have given us.

Flight is one of the oldest of human aspirations, and it is one that all peoples

have shared. They have incorporated visions of flying deities, spirits, and people in their various cosmologies, theologies, and mythic pasts. Yet for all this global interest, the actual achieve­ment of human flight has greatly exceeded the expectations of those who dreamed what flight would give to humanity. They could hardly have conceived a world in which hundreds of millions of people each year journey from their homes to transportation cen­ters designed for aviation, where they enter specialized aircraft to rise several miles off the ground and travel at speeds of hundreds of miles per hour across their countries and around the globe.

Indeed, those people who dreamed of flight largely did so at a time when they (with the aid of horses) could travel no faster than 6 miles per hour (9.7 kilo­meters per hour). This rate of mass mobility remained until the early years of the nineteenth century and the intro­duction of the steam railroad. By the beginning of the twentieth century, the steam locomotive had given people routine mass transportation at 60 miles per hour (97 kilometers per hour).

Then came the airplane, which, by the turn of the twenty-first century, was whisking its passengers over thousands of miles at an average speed of 600 miles per hour (970 kilometers per hour). If current interest in high-speed propul­sion continues, it is possible that our descendents will usher in the twenty – second century at a speed of 6,000 miles per hour (9,700 kilometers per hour)— such is the pace of mass mobility in the aerial age.

The achievement of flight has repre­sented the integration of diverse tech­nologies and disciplines: those of flight itself, such as aerodynamics; those of engineering, such as structures and propulsion; and those of related fields, such as electronics and communications. It was this integration process that took the kite, boomerang, turbine, and fire­work from their first, simple forms to the sophistication of the winged airplane, the helicopter, the jet engine, and the solid-and-liquid-fueled rocket. Even the pioneers (the Wright brothers and rocket scientist Robert Goddard, for example) were masters at blending the various elements into a satisfactory whole.

Human flight was first achieved at the end of the eighteenth century with the invention of hot air and hydrogen – filled balloons. It was only after the invention of the internal combustion engine in the mid-nineteenth century, however, that practical flight became a possibility. Once the airplane and airship had been invented, extraordinarily rapid developments in the field of aviation followed.

At first, several European countries took the lead in the science and techno­logy of flight. The United States, however, was particularly suited to air transportation because of its size. The nation emerged from World War I as the leading industrial power and soon began to dominate the aviation field. By the 1930s, the U. S. aeronautical industry was the largest and most structured in the world. Other nations also produced powerful aeronautical establishments.

This progress in aviation develop­ment was demonstrated in the opening months of World War II. Germany’s blitzkrieg warfare depended heavily on

a core of powerful air striking forces. Air battles between Britain and Germany in 1940 showed how significant the air­plane had become as an instrument of war. The rest of the war that followed, on multiple fronts, revealed the often – surprising power of aircraft in both offensive and defensive combat. In fact, a lack of air power at critical junctures proved to be a more serious disadvantage than any deficits in land or sea power. World War II also highlighted the value of four new technologies that would play a huge role in future aerospace development: radar, the jet engine, the rocket, and the atomic bomb.

In the mid-1900s, flight underwent three remarkable transformations. One was in high-speed aviation, demon­strated by the breaking of the sound barrier in 1947. Another was the appli­cation of the drag-reducing swept wing to jet aircraft. This wing design revolu­tionized both military and civil aviation and led to the rapid global mobility of the present age. The third, in 1957, was the onset of the Space Age, with the launch of the first Earth-orbiting satel­lite, Sputnik 1, by the Soviet Union.

The success of this small sphere hurtling through space overturned the whole aeronautical picture. Today, more than fifty years after that epochal event, it is fair to state that the Sputnik program marked the birth of the Space Age. The product of Sergei Korolev and a team of gifted Soviet designers, Sputnik demonstrated mankind’s ability to place a satellite in orbit around Earth.

As such, the mission anticipated all subsequent satellites and their varied applications. Weather observation, com­munication, strategic reconnaissance, warning, navigation, remote sensing- these are all now taken for granted.

Sputnik marked the onset of a brief but intensive rivalry in space between the United States and the Soviet Union. The stakes were, as is now realized, achievement of the first manned flight to the Moon. It was a race that the United States won, but at significant cost. The U. S. space agency NASA then focused on the Space Shuttle project, another major but costly step. Maintaining the Space Shuttle (in great part to support the creation of the complex International Space Station) proved to be a great challenge that has lasted from the 1980s into the 2000s.

Today, the United States is not alone as a space-travel provider. Commercial
use and privatization of space is increas­ing spaceflight greatly. It is a hopeful sign. Individual entrepreneurs, mirroring early aviation pioneers, are willing to invest their own resources in making space access available for many. Only time will tell how successful their vari­ous space ventures will be.

Today, the world’s goods are largely shipped by air, and the mass mobility of populations depends on air transporta­tion. Aircraft and spacecraft routinely influence the day-to-day activities of humanity. Businesspeople think little of making multiple trips in a single week by air, just as their predecessors relied upon the train. Students and other trav­elers fly across continents and over seas, carrying the influence of their own cul­ture with them to new places. Science and technology, the environment, and the world in which we live are all dependent on the aerospace industry and the global communications it provides.

For all of these reasons, it is well to have this encyclopedia. Broad in scope and straightforward in explanation, it is designed to meet the needs of students and those seeking to understand the history of flight and its functioning in the modern world. Only through works such as this can the youth of today be adequately prepared to face the wonder­ful world that awaits them within Earth’s atmosphere and the extraordi­nary discoveries yet to be made far out in the distant reaches of space.

Dr. Richard P. Hallion, 2008

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ABOUT THE CONSULTANT

Dr. Richard P. Hallion is the former senior advisor for Air and Space Issues, Directorate for Security, Counterintelligence, and Special Programs Oversight at the Pentagon, in Washington, D. C., and a member of the Senior Executive Service. For more than ten years (1991-2002), he was the historian of the U. S. Air Force.

Dr. Hallion is now president of the consultancy group Hallion Associates.

Dr. Hallion has broad experience in science and technology museum development and in research and management analysis. He has served as a consultant to various profes­sional organizations. He also has flown as a mission observer in a wide range of high-performance aircraft.

Dr. Hallion is the author and edi­tor of numerous books, articles, and essays on aerospace technology and military operations. He teaches and lectures widely. His numerous awards include: Citation of Honor, U. S. Air Force Association (1985); Comman­der’s Medal for Public Service, U. S. Army (1988); Louis Bauer Distinguished Lectureship, Aerospace Medical Asso­ciation (1999); Associate Fellow and Distinguished Lecturer, American Insti­tute of Aeronautics and Astronautics (2005); and the Harry B. Combs Award, National Aviation Hall of Fame (2006).

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