Category FLIGHT and M ОТІOIM

After being launched, a spacecraft leav­ing Earth for the Moon or Mars does not need to keep burning fuel. Spacecraft can make use of other methods of propulsion, such as solar sails or ion engines. Once on course and free of Earth’s gravity pull, the engines can be switched off to save fuel as the space­craft coasts through space. This is how the Apollo astronauts traveled to the Moon, a trip that took two-and-a-half days. They fired their engines only to slow down the spacecraft and during their return to Earth.

Although there is no air in space, space is not empty. It contains dust, chunks of minerals, space junk, and streams of radiation flowing out at great speed from the Sun and from other stars.

Stretching into space around Earth is a magnetic field. This magnetism attracts electrically charged particles that form belts, or zones, of radiation. Named the Van Allen radiation belts, these radia­tion zones were unknown until the first U. S. satellite, Explorer 1, encountered them in 1958. The Van Allen belts were the first important scientific discovery made by a spacecraft.

The fastest spacecraft sent from Earth so far have been the solar probes Helios A (1974) and Helios B (1976). Helios B traveled about 150,000 miles per hour (241,350 kilometers per hour) as it orbited the Sun. Although spacecraft are the fastest vehicles ever flown by humans, they are snail-like in space terms, where the distances are unimag­inably immense. The nearest star is 4.2 light years from Earth. So even if a future spacecraft could reach light speed of 186,000 miles per second (299,280 kilometers per second), it would take 4.2 years to get there.

To fly astronauts to Mars and back using existing spacecraft would take eighteen months. Keeping astronauts alive, healthy, and able to work during such a long mission poses great chal­lenges to space science. Humans are not designed for an airless, weightless environment. A manned spacecraft must provide everything needed for human life support-air, water, food, fuel, energy, waste disposal, and exercise. Long periods of spaceflight weaken the body’s muscles. So great are the chal­lenges that some scientists believe that

he Space Shuttle was the world’s first reusable spacecraft and the first spacecraft with wings. The Space Shuttle can carry seven astronauts into space, stay in orbit for about two weeks, and then fly back to Earth to land on an airstrip.

The Shuttle Concept

Until the first Space Shuttle flew in 1981, all spacecraft (manned craft, satel­lites, and space probes) were launched by multistage rockets. Such rockets and the spacecraft they carried could be used just once. Only the spacecraft itself reached space; the discarded rocket stages fell into the sea or burned up in the atmosphere. The Space Shuttle was planned as a more economical vehicle
that could make regular trips into space. It has no rival. The Soviet Buran shuttle spacecraft, similar in appearance, made only one flight, without a crew, in 1988; it was thereafter canceled.

In 1969, a Space Task Group set up by President Richard Nixon’s adminis­tration suggested several new space projects. One was a reusable spacecraft, capable of flying one hundred or more missions. The result was the Space Shuttle, known to NASA as the Space Transportation System (STS). The main contractor was North American Aviation (later part of Rockwell International, now part of Boeing). Other contractors responsible for supplying the engines

О A view inside the Space Shuttle shows the giant engines, the cargo bay, and the flight deck and mid-deck where the astronauts live.

Air

control

thrusters

Electrical system fuel cells

and fuel tanks, were Morton Thiokol, Martin Marietta, and Rocketdyne.

The first Shuttle to fly was Enterprise, which was used for prelimi­nary flight and landing tests from 1977. These tests included flights on top of a modified Boeing 747 airplane. Enterprise never actually went into space. Five Space Shuttles have flown in orbit. The first operational Space Shuttle, delivered to NASA in March 1979, was Columbia, which made its first space flight on April 12, 1981, and remained in service until it was destroyed in a tragic accident in 2003. Challenger, which arrived at Kennedy Space Center in July 1982, was the first Space Shuttle to be lost in an accident, in January 1986. The three Space Shuttles currently operational are Discovery, delivered in November 1983; Atlantis, delivered in April 1985; and Endeavour, which was built to replace Challenger and arrived at Kennedy Space Center in May 1991.

The wings, fin, and stabilizers keep an airplane flying straight and level. A pilot, however, needs the ability to make an airplane turn, climb, dive, and roll. Parts of the aircraft’s wings, fins, and stabilizers are hinged so that they can swivel. These moving parts are called control surfaces. The control surfaces are

the ailerons in the wings, the elevators in the horizontal stabilizers, and the rudder in the vertical fin. When the pilot moves the flight controls in the cockpit, the control surfaces move and change the aircraft’s balance. The aircraft responds by turning, pitching its nose up or down, or rolling.

An aircraft’s ability to produce the amounts of pitch, roll, and yaw the pilot wants is called the aircraft’s response. Different types of aircraft often need a different response. For example, a fast response is crucial for fighter planes in combat. Modern fighters are deliberately designed to be unstable. Flight comput­ers keep a fighter plane under control until the pilot needs to make a fast maneuver, when the plane’s lack of sta­bility enables it to respond instantly to
the controls. Airliners do not need the rapid response of fighters. An airliner is more stable and responds more slowly to its controls.

n aircraft’s tail helps to keep it stable in the air. The tail’s con­trol surfaces make the aircraft climb, dive, and turn to the left or right.

An airplane’s tail acts like an arrow’s feathers or a firework rocket’s long stick. The tail keeps the plane pointing in the right direction, nose first. Without a tail in place, most airplanes would crash to the ground. The Northrop B-2 Spirit stealth bomber, for example, has no tail and is therefore a very unstable aircraft. It only can be flown with the help of a powerful flight computer.

Stabilizers

A typical airplane tail has a vertical sta­bilizer, or fin, that stands up on top of the fuselage, and a horizontal stabilizer, or tailplane, which sticks out from either side of the tail fin. The fin has a moving part at the back called the rudder. When the rudder is turned to the left, the air
flowing around it pushes the plane’s tail to the right, and the aircraft’s nose turns to the left. When the rudder turns to the right, the aircraft’s nose turns to the right.

The tailplane has moving parts at the back called elevators. The elevators con­trol the aircraft’s pitch. When the eleva­tors tilt up, air flowing around them pushes the aircraft’s tail down and brings the nose up. When the elevators tilt down, the aircraft’s nose tips down as well.

Another method for achieving vertical flight uses separate engines for lift and for forward flight. The lift engines are used to get airborne, and then separate forward thrust engines propel the plane normally. Once the plane is flying forward and the wings are generating lift, the lift engines are shut down. The disadvantage of this design is that the aircraft has to carry the dead weight of the lift engines, which reduces its performance.

One example of this type of aircraft is the Russian Yakovlev Yak-38 Forger. It has three jet engines. Two lift engines behind the pilot blow air straight down. The main engine provides thrust from two nozzles behind the wing. These nozzles can rotate to direct the jet exhaust downward to provide extra lift. The Yak-38 serves on Russia’s Kiev class aircraft carriers.

orld War I began in Europe in 1914, and the United States entered the war in 1917. Remembered for the terrible slaughter of trench warfare on the Western Front, the “Great War,” as World War I became known, was the first war in which air­planes played an important part.

LEARN-EARN

О A World War I poster encourages volunteers to enlist in the Air Service, part of the U. S. Army. At the time, there was no separate U. S. Air Force. The poster reflects the aircraft of the period, including airships.

The Role of Aircraft

Until 1914, military strategists regarded command of the sea as the key factor in international warfare. Britain, Germany, and the United States had the biggest navies. When World War I began, air­planes were still a novelty. The fastest airplane had a top speed of only 100 miles per hour (160 kilometers per hour) and a range of about 100 miles (160 kilometers) before needing to refuel.

In the nineteenth century, balloons and airships had been used in wars, mostly for observation and for evacua­tion of civilians. The military had yet to find uses for the airplane. In 1912, Britain had set up a Royal Flying Corps, but it had very few aircraft. Germany had the largest air force, with more than 200 airplanes plus Zeppelin airships. The U. S. Army had purchased its first air­planes in 1913. No nation had assembled a large air force.

In the four years of World War I (1914-1918), the airplane became a much more formidable weapon. Fighter planes battled in aerial combats called dogfights. For the first time, cities were bombed from the air by airships and air­planes. The warring nations formed air forces or aviation divisions within their armies and navies. War would never be the same again.

Dates of birth: Wilbur: April 16, 1867; Orville: August 19, 1871.

Places of birth: Wilbur: Millville, Indiana; Orville: Dayton, Ohio.

Died: Wilbur: May 30, 1912; Orville: January 30, 1948.

Major contribution: Achieved the first sustained, powered, controlled airplane flight; built the first practical powered airplane; built the first practical passenger-carrying airplane.

Awards: Orville: Collier Trophy.

n December 17, 1903, Wilbur and Orville Wright flew the first sus­tained, powered, controlled air­plane flight at Kitty Hawk, North Carolina. The Wrights continued experi­menting with airplane designs and made several important advances. They helped promote aviation across the United States and in Europe.

Early Life

The Wright brothers were the sons of Milton and Susan Wright. Their father was a church minister. Years after their success, the Wrights said they first became interested in flying in 1878 when their father brought home a toy helicopter powered by a rubber band. Intrigued when the toy flew, the boys played often with it and experimented by making their own versions of it. Their mother, who often made toys and

household appliances herself, encour­aged the brothers’ interest in flight.

Wilbur graduated from high school, but before starting college he suffered a serious injury while playing hockey. He remained at home, helping his father with church business and caring for his sick mother until her death in 1889. During this time, Wilbur read constantly.

By the time their mother died, Wilbur’s younger brother Orville had persuaded Wilbur to join him in opening a print shop in their hometown of Dayton, Ohio. The brothers began pub­lishing a small newspaper, but they failed to make money with the paper and eventually closed the business. In 1892, the brothers opened a successful bicycle shop where they built, sold, and repaired bikes.

Modern aerobatic aircraft can per­form maneuvers impossible for an ordinary airplane, such as torque rolls (rolling and sliding backward at the same time) or lomcevaks (tumbling end over end). Aerobatic

О The U. S. Navy’s Blue Angels, using F/A-18 Hornets, perform aerobatic movements at an air show in 2006.

planes are strong but very light in rela­tion to the power of their engines. Most use piston engines and propellers.

One outstanding aerobatic airplane is the U. S. Pitts Special. The first Pitts flew in 1947, and since then Pitts Specials have dominated aerobatic competitions. The later versions of this little plane remain close to the original design.

Formation teams perform their dis­plays with as many as sixteen aircraft, although a team of nine or ten is more usual. During a per-formance, aircraft change formations a number of times. They split up into smaller groups, fol­lowing the instructions of the team leader by radio. Pilots often use colored smoke trails to highlight the patterns they are flying.

Famous aerobatic teams include the Blue Angels of the U. S. Navy, the Thunderbirds of the U. S. Air Force, and the Red Arrows of the British Royal Air Force. Unlike other aerobatic performers, military teams usually fly jet planes. These planes fly faster than propeller planes and need more space to display their formations. The Thunderbirds fly the F-16 Fighting Falcon that has a top speed of 1,300 miles per hour (2,092 kilometers per hour).

Accidents are rare, but aerobatics are demanding. Pilots practice constantly to perfect new formations and sequences. They also must keep physically fit to cope with the stress of aerobatics, which subjects their bodies to strong g-forces (acceleration measured as multiples of the force of gravity at Earth’s surface).

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PATTY WAGSTAFF

Born in 1951 in St. Louis, Missouri, Patty Wagstaff flew with the U. S. aerobatics team from 1985 to 1996. She was the first female U. S. National Aerobatic champion, a title she won three times. Wagstaff was International Aerobatic champion in 1993. In 2004, she was elected to the National Aviation Hall of Fame. The Goodrich Extra 260 plane flown by Patty Wagstaff in the 1990s is displayed at the Smithsonian Institution’s National Air and Space Museum. Wagstaff has flown at air shows all over the world and says she likes the precision of aerobatics. "I like flying a perfect loop. . . a per­fect maneuver."

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SEE ALSO:

• Aerodynamics • Barnstorming

• Gravity

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The aerospace industry has cut thou­sands of jobs in recent years, however, because of a drop in orders due to finan­cial problems in the airline industry. A decline in airline business followed terrorist attacks on the United States in 2001. Rising fuel prices also hit airlines hard, and several major U. S. airlines have filed for bankruptcy in recent years.

The aerospace industry has also been troubled by disputes between the United States and Europe over government sub­sidies (payments to offset the cost of developing new aircraft). Boeing, facing stiff competition from the new, giant

Airbus A380, has complained to the World Trade Organization about low – interest loans made to Airbus by the European Union.

The space industry has been hit by uncertainty over plans for the future of manned flights. Programs such as the International Space Station (ISS) and a replacement vehicle for the Space Shuttle, however, continue to create demand and challenge the industry’s best workers. Aerospace manufacturers are facing another challenge, posed by envi­ronmental concerns—how to build quiet and fuel-efficient aircraft for the future.

N

SEE ALSO:

• Aircraft, Commercial • Aircraft,

Military • Boeing • Curtiss, Glenn

• Wright, Orville and Wilbur

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Aileron and Rudder

he ailerons and rudder are two of the three control surfaces on an airplane (the third is the elevator). They are the moving parts that steer a plane through the air. The ailerons are panels in the trailing (back) edges of the wings. The rudder is part of an airplane’s tail fin.

Pilots use the ailerons and rudder together to make a turn. They learn how to steer their aircraft smoothly through a turn with the nose pointing in the right direction.

A good air traffic controller needs to have spatial awareness and mathe­matical abilities. Above all, a con­troller must stay calm under pressure.

He or she must be able to absorb data, assess a situation accurately, and make the right decision quickly. Fitness, good vision and hearing, and a clear radio speaking voice are also essential. A controller should be a good team worker because safe air travel requires cooperation from many people. Air accidents are rare, but near misses sometimes do occur. After the attacks of September 11, 2001, terrorism brought a new dimension of risk, adding to U. S. air traffic controllers’ responsibilities.

In 1981 air traffic controllers in the United States went on strike. They were protesting their increasing workload and the stress and dangers of handling more airplanes every year. The federal government dis­missed 10,000 controllers. To reduce pressure, however, a flow control system was introduced. Under this system, an airliner could not leave an airport unless landing space was available at its destination airport at the time it was due to arrive. This eased the stress on controllers who were handling the holding stacks of airplanes waiting to land.

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on a highway. The difference, of course, is that aircraft travel much faster than cars and fly at different heights. Several aircraft may be flying over an airfield while other planes are preparing to land or take off below. For safety, all these aircraft must keep safe distances apart, both vertically and horizontally. The normal vertical distance between air­craft, known as safe vertical separation, is 1,000 feet (305 meters) below 29,000 feet (8,840 meters) and 2,000 feet (610 meters) at altitudes above 29,000 feet (8,840 meters). For planes at the same height, a distance of at least 10 miles (16 kilometers) apart is regarded as safest.

In the United States each ARTCC’s zone is divided into smaller sectors. Around airports, the airspace comes under Terminal Radar Approach Control (TRACON). Each TRACON covers rough­ly a 50-mile (80-kilometer) radius of air­space, and within each airspace is at least one airport. Each airport also has its own airspace, with a radius of 5 miles (8 kilometers). Around some busy inter­national hubs, one main computerized center handles all traffic. London, for example, has one main center that con­trols air traffic in and out of the city’s five major airports.

At a small airport, controllers may have control of aircraft on the ground and in the air around their airfield. Small flight service stations (FSS) help and advise private pilots flying in coun­try districts or from small airfields.

At a larger, busier airport, different types of controllers may be assigned to

various tasks. Tower con­trollers keep a visual watch on aircraft as well as using radar. Approach controllers follow the movements of airplanes approaching and leaving the airfield, usually up to a distance of 50 miles (80 kilometers) and to a height of 10,000 feet (3,050 meters). Area controllers are responsible for planes flying at higher altitudes.

The duties of an air traffic controller include using the radio to pass instructions to pilots about takeoff and landing and to relay weath­er information. Controllers use radar to track airplanes during their flights and plot the locations of aircraft on charts (maps). They check aircraft speed, direction, and altitude and keep a record of all movements and commu­nications. Computers are vital to air traffic controllers for processing and accessing information.