Category FLIGHT and M ОТІOIM

The simple HHMU gas guns led to the bigger maneuvering units worn by astronauts in later years. One of these was NASA’s manned maneuvering

unit (MMU). The unit clipped onto the back of an astronaut’s spacesuit. The MMU enabled the astronaut to fly freely in space, without a tether, like a one – person spacecraft.

The MMU was propelled by puffs of nitrogen gas from twenty-four thrusters pointing in different directions. It was flown by means of two hand controllers. The controller in the astronaut’s right hand was used for pitch, roll, and yaw motions. The left controller moved the astronaut in a straight line forward and back, up, and down, or left and right. The MMU also could fire jets to keep the astronaut in the same position.

MMUs were used by Space Shuttle astronauts between 1984 and 1986. Cosmonauts at the Russian Mir space station tested a similar jetpack for per­forming extra-vehicular activity (EVA).

After the MMU, NASA developed a much simpler space maneuvering unit. Astronauts working outside the Space Shuttle or the International Space Station wear a device called the simplified aid for EVA rescue, or SAFER. Tested in space for the first time

in 1994, the unit fits around an astro – propulsion. The SAFER is much smaller naut’s life-support backpack. Like the than the MMU and it holds less gas, so it MMU, the SAFER uses nitrogen gas for is intended for emergency use only.

When a plane cruises at a steady speed, the thrust of its engines forcing it for­ward is exactly balanced by drag pulling it backward. If the drag can be reduced, the plane can go faster or farther or burn less fuel.

One way to reduce drag is to make the wings thinner. The Lockheed F-104 Starfighter was a very fast fighter built in the 1950s. It had very thin wings to reduce their drag and make the plane as fast as possible. In fact, its wings were so thin and the leading edges were so sharp that soft covers had to be fitted to them on the ground to protect engineers from injuries if they walked into a wing.

Gliders

Gliders have long, thin wings that create a lot of lift and a slim, streamlined body that causes little drag, so they have very high L/D ratios.

For gliders the L/D ratio is the same as the glide ratio. This is the distance a glider flies forward compared to the height it loses. A glider with a glide ratio of 70:1 flies 70 feet (21 meters) forward for every 1 foot (0.3 meters) it descends.

It is important to know the L/D ratio of a powered aircraft, because it tells the pilot how far the plane can glide before it has to land if the engines fail. While it is gliding, drag is slowing it down. As it slows down, its wings produce less lift, so it loses height.

In 1982, a Boeing 747 flew into a cloud of ash rising from a volcano in Indonesia. The ash damaged the engines.

All four engines failed at an altitude of 37,000 feet (11,278 meters). With an L/D ratio of 15:1, the 747 could glide a distance equal to fifteen times its altitude, or up to about 105 miles (170 kilometers). Luckily, the crew was able to restart three of the engines and land the airliner safely.

The Space Shuttle returns to Earth without engine power and glides down to a landing. Compared to an airliner or glider, the spacecraft has a very poor L/D ratio. It drops like a stone as it glides, approaching the runway at an angle six times steeper than that of an airliner.

issiles are self-propelled weapons that fly toward their targets at high speed, armed with an exploding warhead. There are many different types of missiles.

The Basic Types

Small missiles are used for attacking tar­gets, such as tanks, just a few hundred or thousand feet away. These small bat­tlefield missiles used by armies are also called tactical missiles. There also are longer-range missiles carried by ships and helicopters for attacking enemy ships, aircraft, and land targets. The biggest and most powerful missiles can fly thousands of miles and do enormous damage to a whole city. These missiles are known as strategic missiles.

Nearly all missiles have a guidance system that steers them toward their tar­gets. For this reason, they are called
guided missiles. There are different types of guidance systems. Some use the heat of the target (for example, the heat gen­erated by the jet exhaust of an enemy fighter plane). Other guidance systems are radar seeking, using the radar reflec­tion of an oncoming missile to find and destroy it. Missiles aimed at a stationary target on the ground can use GPS as their guidance system.

Missiles also are defined by where they are fired from and what their target is. Surface-to-air missiles (SAMs) are launched from the ground at aircraft. Air-to-ground missiles (AGMs) or air-to – surface missiles (ASMs) are fired by air­craft at targets on the ground.

Air-to-air missiles (AAMs) are fired by aircraft at other aircraft. The AIM-9 Sidewinder is a short-range missile used by fighter planes in combat with each other. AIM stands for air intercept mis­sile. When a Sidewinder is fired, its solid fuel rocket accelerates it to more than twice the speed of sound. Fins on the nose and tail provide lift and steer the mis­sile. The missile’s nose

О A view of the wing of a U. S. Navy Hornet shows two laser-guided bombs and (on the outside) an AIM-9 Sidewinder missile. The Sidewinder is an air – to-air missile, which means it is used by aircraft to attack enemy aircraft.

The world’s first ballistic missile was the V-2, developed in Germany during World War II. It stood 47 feet (14 meters) high and weighed about 29,100 pounds (13,200 kilograms). The V-2’s nose contained 1,600 pounds (about 725 kilograms) of explosives. Its rocket

engine, burning alcohol and liquid oxygen, boost­ed it to a height of about 50 miles (80 kilometers), and then the V-2 fell toward its target, up to 200 miles (320 kilometers) away. The V-2 arrived with­out warning because it flew faster than the speed of sound. Even if a V-2 was spotted, it was flying too fast to be shot down.

The V-2 was not a very accurate weapon. It could be fired at something as big as a city with a good chance of hitting it, but it could not be counted on to hit smaller targets, such as bridges or runways. About 4,000 V-2s were launched during the war-more than 1,000 fell on London. After the war, the United States and the Soviet Union captured scores of unused V-2 rockets. Many of the ballistic missiles and space rockets built in the 1950s were based on the V-2.

О A V-2 rocket is prepared for launch by technicians in Germany in the early 1940s.

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contains an infrared (heat) seeker. This detects the heat of the target plane and steers the missile toward it.

Kings and emperors often appear in leg­ends about flying. The earliest known story of a flying person-about 4,500 years old-is the legend of King Etana of Sumer in Mesopotamia (modern-day Iraq). The king and his wife were not able to have a child, and he desperately wanted an heir. Following the instruc-

tions of the sun god, he freed a captured eagle. The bird carried King Etana to heaven, where he begged the goddess Ishtar for a child. She gave him a plant that both he and his wife ate, and the treatment worked.

Nearly as old is the Chinese legend of the emperor Shun. He used two over­sized hats to fly. Once he employed this device to escape a burning tower. On another occasion, he used it to fly around his empire.

The Persians also told of a king who flew. The vehicle that King Kai Kawus used was of ingenious design. Workers attached long poles to the four corners of this throne. They tied meat to the top of each pole, and at the bottom of each pole they chained an eagle. When the eagles grew hungry, they beat their
wings in an effort to reach the meat. That motion carried the throne aloft. This method worked, and the eagles car­ried the king into the sky. Unfortunately, they grew tired and stopped flapping their wings. When that happened, the throne tumbled to the ground.

A similar story involves the Greek conqueror Alexander the Great. He tied hungry griffins to poles attached to his throne. Griffins were half lion and half eagle. Alexander’s story ends with a more direct moral than that of Kai Kawus, however. His vehicle stayed in the air for a week and brought him near the heavens. An angel then appeared and asked him why he wanted to see the
heavens when he did not yet understand everything about life on Earth. Humbled, the conqueror returned to land.

Britain also has an ancient legend of a king who flew. King Bladud, who reigned in the ninth century b. c.e., had great intelligence and practiced magic. He fashioned a pair of feathered wings and launched himself into the air.

However, the king’s flight ended in dis­aster. In some versions of the story, he plunged to his death. In others, he slammed into a wall. Either way, he lost his life and his kingdom, which was then inherited by his son—Lear. King Lear then became the subject of another leg­end, which was immortalized in a tragic play by William Shakespeare.

parachute is a canopy that slows the fall of an object or person through the air. The word parachute means “against a fall.”

Parachutes have saved the lives of many pilots who needed to eject from damaged airplanes. Parachutes are used to drop supplies and paratroopers (para­chuting soldiers) from airplanes. Sports parachutists enjoy freefall skydiving. Yet another use for a parachute is as an air­brake, to slow an airplane, spacecraft, or other vehicle as it lands.

A personal parachute is packed in a bag or body pack worn by the para­chutist and attached to a strong harness or supporting rig. After exiting the air­craft, the parachutist opens the para­chute by pulling a handle called the rip­cord. Parachutes also can be opened automatically. When a pilot ejects from a jet plane, for example, the ejector seat mechanism opens the parachute. Brake parachutes for slowing down an airplane are stowed in the tail and open only after the plane has touched down on the runway. A spacecraft parachute opens after reentry into the atmosphere. Other brake parachutes may be automatic or manually deployed.

The canopy is made of a tough, light fabric-silk was traditional, but nylon and other synthetic materials are used today. The traditional shape for a para­chute canopy was a circle, but modern parachutes are usually square or rectangular. The parachutist’s harness

is attached by straps, called risers, to suspension lines around the edge of the canopy. As parachutists float to the ground, they can make turns by tugging on steering lines.

ollution is the process of making the environment dirty, dangerous, or in other ways unpleasant or unhealthy for people, animals, and plants. Flying contributes to pollution through the emissions from airplane engines and through noise and environ­mental damage around airports.

Transportation is a major source of air pollution in the United States and other industrial nations. Jet engines, like automobile engines, burn carbon-based fuel. During the burning process or com­bustion, airplane engines give off car­bon monoxide, carbon dioxide, hydro­
carbons (compounds of carbon and hydrogen), and nitrogen oxides (com­pounds of nitrogen and oxygen). These substances are all pollutants, and too many of them in the atmosphere can have damaging effects on people, on animals, on plants, and even on build­ings. Polluted air is unhealthy to breathe. Heavy concentration of pollu­tants around cities can form smog, reducing visibility and air quality and endangering the health of people.

Scientists believe that carbon-based pollutants are causing damage to Earth’s atmosphere. A buildup of carbon diox­ide gas in the atmosphere from burning fossil fuels-such as gasoline and avia­tion fuel-is thought by many experts to contribute to the greenhouse effect. The gases trap heat from sunlight, therefore contributing to global warming and climate change.

High-flying jet aircraft emit those gases close to Earth’s surface and at higher altitudes. The primary gas in jet engine emissions is carbon dioxide, which can linger in the atmosphere for up to a hundred years. Aviation emis­sions account for up to 4 percent of all global carbon dioxide emissions from the burning of fossil fuels. Carbon diox­ide combined with other airplane exhaust gases could be having a much greater impact on the air than carbon dioxide alone.

Most legislation passed in recent decades to cut air pollution has been directed at industry and automobiles. With aviation growth at around 5 per­cent a year, however, the development of cleaner aircraft engines is vital.

Airports also are a source of pollu – tion-not simply because of the number of airplanes using them, but because a busy airport draws in thousands of cars and trucks every day. Airport buildings and handling facilities consume a lot of energy and produce a lot of waste. Even the chemicals used to de-ice airplanes in winter pose a pollution risk to the soil and the water cycle.

NOISE POLLUTION

As air traffic increases, there are concerns about noise pollution. Anyone who has stood on a runway close to a jet plane taking off knows that it is very noisy. The loudness is measured in decibels. A jet plane taking off can reach 130 decibels. Supersonic planes also make a sonic boom. Protests about the boom ended airline plans to fly the Concorde on transcontinental super­sonic flights in the 1970s. Modern turbofan engines are more efficient and less noisy than the engines of fifty years ago, but many airports suspend flights at night so that local residents can sleep undisturbed.

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Some campaigners argue for cuts in flights or at least increased airport and airline taxes-and thus higher fares – to reflect the true environmental cost of flying. Aircraft manufacturers respond that new airplane engines are becoming increasingly efficient and clean. They also say the introduction of larger air­planes means fewer flights, less fuel burned, and therefore less pollution.

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SEE ALSO:

• Aircraft Design • Airport • Engine

• Fuel • Future of Aviation

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Solid-fuel rockets are the simplest and oldest type of rockets. Aircraft have been armed with solid-fuel rockets since World War I, when they were used to attack airships and observation bal­loons. Rockets fired from one aircraft at another aircraft are called air-to-air rockets. The airships and balloons were filled with hydrogen, which burned if a flaming rocket flew into it. The problem was that the planes of the day also were made of flammable materials, so firing rockets from them was dangerous. The rockets also were inaccurate and rarely hit their targets.

Small air-to-air rockets were used again in World War II. They enabled fighters to attack bombers without com­ing within range of the bombers’ guns. These small rockets were unguided-they were aimed simply by pointing the

О The Space Shuttle has two solid rocket boost­ers (SRB) that are strapped to its external fuel tank. The SRB are discarded about 2 minutes after liftoff, and they fall back to Earth to be retrieved and reused.

Robert Hutchings Goddard was an American scientist and inventor who developed the modern liquid-fuel rocket. He received patents for a liquid-fuel rocket and a two – stage rocket in 1914. In 1919, Goddard wrote a paper called "A Method of Reaching Extreme Altitudes," in which he talked about sending a rocket to the Moon. He was ridiculed at the time for even suggesting such a crazy idea. In 1926, Goddard suc­ceeded in building and launching the first liquid-fuel rocket. Powered by gasoline and liquid oxygen, the small rocket rose to a height of 41 feet (12 meters). Goddard went on to build bigger and more powerful rockets. Some of them climbed higher than

9,0 feet (2,740 meters) and went faster than the speed of sound. Goddard was the first person to steer a rocket by using vanes in the rocket exhaust, and he designed the first gyroscopic systems for guiding rock­ets. NASA’s Goddard Space Flight Center is named in his honor.

C Robert Goddard displays his liquid oxygen-gasoline rocket before its successful launch in 1926.

whole plane. In the 1950s, air-to-air rockets were replaced by guided missiles.

Solid-fuel rockets are used to help launch spacecraft. Space launch rockets are liquid-fuel rockets, but they can be made more powerful by strapping solid- fuel rockets around them. The solid rock­ets provide extra power for liftoff. Extra rockets used like this are called boosters. The Space Shuttle is launched with the
help of two solid rocket boosters (SRB). They burn powdered aluminum fuel with ammonium perchlorate oxidizer. The propellants are mixed as liquids and then set hard in a mold. A hole runs through the center of the rocket. When the propellants are ignited, they burn from the inside out. Once solid-fuel rockets have been lit, they cannot be turned off.

In the spring of 1909, Sikorsky built his first real helicopter. However, the machine would not fly. Another version failed to fly the following year, and Sikorsky decided to abandon the effort. As he later explained, “I had learned enough to recognize that with the exist­ing state of the art, engines, materials, and—most of all—the shortage of money and lack of experience. . . I would not be able to produce a successful helicop­ter at that time.”

Sikorsky turned his attention to designing airplanes, producing several models and flying them himself. In 1911, he earned an international pilot’s license, becoming just the sixty-fourth person in the world to have one. That year, Sikorsky’s S-5 plane set records by carrying three people more than 30 miles (48 kilometers) at 70 miles per hour (about 113 kilometers per hour). Another of his planes won an award at an air show the next year and took first prize in a competition held by the Russian armed forces. This success earned Sikorsky a job with a Russian company, where he worked on manufac­turing airplanes.

In 1913, Sikorsky produced a new design he called the Grand. This large airplane was powered by four engines – the first flying machine to have more than one. It also was the first to have the pilot and passenger areas fully enclosed. The Russian army used several dozen aircraft of this design as bombers during World War I (1914-1918).

Russian participation in the war ended when communists took control of the nation’s government and pulled the country’s troops out of the conflict. Sikorsky left his homeland in 1919 and eventually reached the United States.

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.

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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.