Category FLIGHT and M ОТІOIM

Spaceflight has a good safety record, but there have been fatal accidents involv­ing astronauts. The first person to be killed during a mission was Soviet cos­monaut Vladimir Komarov in April 1967. Veteran of an earlier flight in the three-man Voskhod 1, Komarov was fly­ing alone in the new Soyuz craft in 1967. It seems the spacecraft began to spin while still in orbit and then over­heated when trying to reenter the atmosphere. Komarov was killed during reentry.

Three U. S. astronauts were trapped and killed in the Apollo 1 fire during ground tests in January 1967. They were Gus Grissom, Ed White (the first American to “walk” in space, in June 1965), and Roger Chaffee.

The worst fatalities to U. S. astronauts involved the Space Shuttle, first flown with astronauts on board in 1981. On January 28, 1986, the Space Shuttle Challenger broke up shortly after liftoff. All seven astronauts were killed. After modifications, the Space Shuttle returned to space, but tragedy struck again on February 1, 2003. This time it was Columbia, nearing completion of its twenty-eighth mission. During its descent, the spacecraft disintegrated high above Texas. Again, all seven astronauts on board died.

Astronauts do not appear to suffer any serious health consequences from short flights. Over time, however, the absence of gravity affects the human body. Astronauts find that their muscles

waste and bones weaken during flights lasting weeks or months. Cosmonaut Yuri Romanenko returned to Earth in 1987 after 326 days in space, aboard the Soviet space station Mir. He found his calf muscles had shrunk 15 percent in spite of workouts on a treadmill and exercise bike.

During periods of prolonged weight­lessness, astronauts grow 1 to 2 inches (2.5 to 5 centimeters) taller because the bones in their spines spread apart. Back on Earth, the bones close up again, and the astronauts soon return to their normal height.

After World War I ended in 1918, there were a lot of ex-military planes for sale and plenty of veter­an pilots looking for jobs. Some of these pilots took up stunt flying and became barnstormers.

The most popular plane they flew was the Curtiss JN-4 Jenny, a wartime training airplane. Pilots could buy a Jenny and fly wherever they wanted to offer flying displays and rides.

Groups of pilots formed traveling shows, or flying circuses. Well-known groups included Jimmy Angel’s Flying Circus, the Five Blackbirds, the Flying Aces, and the Ivan Gates Flying Circus. Ivan Gates toured the United States and hired daring fliers such as Clyde “Upside-Down” Pangborn and Diavalo, “Supreme Daredevil of the Air.” Women barnstormers included Bessie Coleman, the first African American woman pilot; Gladys Ingle, who shot arrows from a bow while wing walking; and Mabel (or Mable) Cody, whose specialty was danc­ing on the wing. Charles Lindbergh, the first person to fly the Atlantic solo, and Wiley Post, the first to fly around the world solo, both spent time flying as barnstorming pilots.

Barnstorming made some pilots wealthy, but it was a tough, dangerous life. Finding fuel and parts for airplanes was not easy in rural areas, and planes
were not always safe to fly. Pilots trav­eled long distances, often going without sleep for days at a time. There were fatal accidents. Bessie Coleman was killed while practicing for a show. Lincoln Beachey crashed into the San Francisco harbor, and Ormer Locklear was killed flying a stunt for a Hollywood movie.

In 1927, the federal government tightened aviation laws to stop danger­ous stunts and make sure that airplanes were properly maintained. The supply of cheap Jenny planes dried up, and the barnstorming era came to an end. Aerobatics and wing walking, however, can still be seen today at air shows.

SEE ALSO:

• Aerobatics • Coleman, Bessie

• Curtiss, Glenn • Lindbergh, Charles

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Bell X-1

Type: Rocket-powered research airplane.

Manufacturer: Bell Aircraft Corporation. First flights: January 19, 1946. (unpowered); December 9, 1946 (powered).

Primary use: Supersonic testing.

he Bell X-1 was the first piloted aircraft to fly faster than the speed of sound in level flight. The flight took place on October 14, 1947.

Landing can be tricky, especially if a bird is aiming to perch on a twig or tele­phone wire. To slow down, a bird uses its tail as a brake, spreading the tail feath­ers to increase drag. Its body adopts an upright position, and the legs swing forward to absorb the shock of impact, just as an airliner lowers its landing gear. The bird beats its wings to main­tain control and uses backbeats (similar to an airline pilot using reverse thrust on a plane’s engines) to slow down. Its feet reach out to get a firm grip on the chosen landing place.

Bigger birds often take a step or two on landing to regain balance, folding their wings as they complete the land­ing. Water birds come down rather like seaplanes, using their feet as water skis as the water slows them down. Some birds, such as fulmars and albatrosses, spent most of their lives flying over the ocean-even sleeping on the wing-and come to land only to breed.

Hunting birds use a variety of differ­ent techniques to descend when they are hunting prey. A buzzard flies high in
circles before swooping down to attack. A peregrine falcon launches itself on its target in a high-speed dive while it folds in its wings to reduce wind resistance. Some birds, such as gannets and boo­bies, dive straight into the ocean to catch fish.

In the late 1940s and early 1950s, air forces switched from propeller-driven bombers to jet bombers, such as the U. S. B-47 and British Canberra (built in the United States as the B-57). Both the

United States and the Soviet Union built fleets of very large strategic bombers, designed to carry atomic bombs as well as conventional high explosive bombs. The U. S. Air Force, now a separate arm of the military, set up Strategic Air Command (SAC) in 1946. By 1953, SAC had over 1,000 aircraft. These included the B-36, a giant with six propellers and four jet engines that gave it a speed of 439 miles per hour (706 kilometers per hour).

During the Cold War of the 1940s to the 1980s, Soviet and Western air forces competed in an arms race to build better, faster, and harder-to-catch bombers. Interesting planes from this era include the British Avro Vulcan— a large delta-wing airplane—and the Soviet Tu-95 Bwar, which was the last big bomber with pro­pellers. Some people argued that the age of the bomber was over and that guided missiles were the weapons of the future. Jet bombers flew twice as high and twice as fast as bombers in World War II, but they were still vulnerable to missiles—so why risk pilots’ lives when unmanned missiles could be used instead of bombers?

The success of the B-52 proved that the bomber was still a power­ful weapon. Originally planned as a turboprop bomber in 1948, the B-52 was fitted with jet engines. More than fifty years after it first

flew, it is still in service. In the Vietnam War, B-52s were used alongside smaller, faster airplanes such as the F-4 Phantom and the F-105 Thunderchief, which were able to carry a combination of bombs and missiles.

Building bombers is an expensive business, and many promising designs never get beyond a prototype. The delta­wing B-58 Hustler of 1960 was the first supersonic bomber, but only 116 of them
were built. Even fewer XB-70s were manufactured. First flown in 1964, and able to fly at three times the speed of sound, the XB-70 was canceled before it even got into production. It is unlikely any more big bombers will be built. The need in the twenty-first century is for multi-purpose airplanes that can perform a variety of tasks-dropping bombs is just one of them.

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SEE ALSO:

• Aircraft, Military • Airship

• Mitchell, Billy • World War I

• World War II

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When a plane is flying over an ocean far away from land, pilots used to endure the hissing, crackling noise of their HF radio constantly in case anyone tried to contact them. There is now a system that does the listening for the pilot. When controllers want to contact a pilot, they send a radio signal to the plane. Each aircraft has its own address code. Many airplanes may receive the signal, but the system in only one specific plane recog­nizes the address code and alerts the pilot. It sounds a chime and flashes a light in the cockpit. This tells the pilot that someone is trying to contact that particular plane.

Even when HF radio is being used for long-distance communication, an air­craft’s VHF radio is not switched off. Pilots leave it on and listen for messages from pilots in nearby aircraft. A pilot who suffers serious turbulence, for example, can warn other pilots so that they can find a way around it.

Commercial pilots also can send and receive short text messages. They use this for standard messages, such as weather reports. The messages appear on a screen and can be printed out on paper using the cockpit printer.

The amount of information sent and received by pilots and aircraft has increased over the years, and it will con­tinue to increase. In the future, aircraft may be able to use broadband links that can transmit live video from the cockpit and cabin, as well as giving the crew and passengers access to the Internet during a flight.

In the late twentieth century, with the development of ever smaller electronic systems, the military saw the potential of unmanned aerial vehicles (UAVs) as spy planes. A drone could be fitted with cameras and modern guidance systems to fly on missions over territory where it might be risky to send a piloted airplane. With a drone, there was no risk of a pilot being lost if the vehicle was shot down.

Drones do not have the same limita­tions as people-they do not get tired or hungry—so they can stay in the air for many hours. A solar-powered drone could, in theory, stay in the air for weeks. Modern drones are very small and some can fly low—sneaking around hills rather than flying over them, which makes them hard to spot on radar.

Whereas early drones were always controlled by a person on the ground, modern drones can fly on their own, using built-in control and guidance systems. In the future, drones may be capable of decision making, replacing the human pilot altogether, but this type of technology is still far off.

The turbojet is the simplest jet engine. Air entering the engine is compressed by spinning fans in what is called a com­pressor. The compressed air flows into the engine’s combustion chamber. Here, fuel is sprayed into the air and burned.

The hot gas produced by the burning expands and forces its way out through the back of the engine. On its way out, the jet of hot gas rushes through anoth­er set of fans, called a turbine, and makes them spin. The spinning turbine drives the compressor at the front of the engine. Turbojets are best suited to air­craft flying at about twice the speed of sound. They are also very noisy, so tur­bojets are not used much today.

Most of the jet engines that power airliners and military aircraft today are turbofans. A turbofan engine has a fan at the front. The fans at the front of the engines that power the biggest airliners are enormous. The fan works like a pro­peller with lots of blades. It is powered by a turbine inside the engine. Only a small fraction of the air that goes through the fan enters the engine. Most of the air from the fan is blown around the outside of the engine. This big mass of air moving slowly around the engine
provides most of the engine’s thrust. It also enables turbofans to be quieter than turbojets. Turbofans work best in air­craft flying at 250-1,300 miles per hour (402-2,092 kilometers per hour).

Turbine engines also power some slower planes with propellers. A turbine engine with a propeller is called a turbo­prop. A turbine inside the engine powers the propeller. Turboprops work best for aircraft flying at up to about 450 miles per hour (724 kilometers per hour).

All but the smallest helicopters are now powered by turbine engines. These engines are called turboshafts. A tur­boshaft engine uses the jet of gas from the engine to spin a shaft. The spinning shaft drives the helicopter’s rotors.

Fighter planes sometimes have to make extremely tight turns in combat. The acceleration forces caused by these tight turns are often called g-forces because they are measured by comparing them to the force of gravity at Earth’s sur­face. An acceleration force equal to Earth’s surface gravity is 1g. A force twice as strong as this is 2g, and so on up the g-force scale.

The human body can survive g-forces as high as about 40g, but only for a brief time. People who ride on the most extreme theme park rides normally experience acceleration forces of up to about 4g. Fighter pilots train to withstand g-forces up to about 9g.

Forces as strong as 9g pull blood from a pilot’s head down into the body and legs. Without any protective cloth­ing or training, the pilot would faint from lack of blood in the brain. This type of fainting is also called g-loc, which stands for g-induced loss of conscious­ness. Pilots get some warning of g-loc
because the shortage of blood in their head causes problems with their vision.

Fighter pilots protect themselves from g-loc by wearing an anti-g suit. In a tight turn, air is pumped into the suit’s body and legs. It squeezes the pilot’s body and legs to stop blood from drain­ing down out of his or her head. Pilots also tense the muscles in their bodies to push more blood up into their heads, but this straining maneuver is very tiring. Pilots can be helped by one more system: Oxygen-rich air is forced into their lungs through a facemask. Air also must be pumped into an inflatable vest, which presses the pilot’s chest with equal force.

Fighter pilots can experience nega­tive g-forces, the forces that act in the opposite direction to gravity. A negative g-force forces extra blood up into a pilot’s head. This causes an effect called red-out, because the pilot’s vision turns red. Pilots can only withstand negative g-forces of about -2g or -3g at most.

UNITS OF FORCE

The units used for measuring force include the newton and the pound force. The newton is the internation­al unit of force. It is the force needed to make a mass of 1 kilogram accel­erate at 1 meter per second squared (or per second per second). This force is roughly the same force as the weight of a 3.5-ounce (about 100- gram) object-a small apple, for exam­ple. The pound force is the weight of a mass of 1 pound (0.454 kilogram).

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SEE ALSO:

• Gravity • Jet and Jet Power

• Laws of Motion • Lift and Drag

• Thrust • Weight and Mass

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Late in 1961, NASA chose Glenn to pilot the first American orbital flight. Getting that flight off the ground became a chal­lenge, however. The launch was delayed by problems with the booster rocket and by bad weather. There was even a brief scare over Glenn’s health when he was exposed to children who had the mumps, a disease Glenn had never had. Luckily, he did not become infected.

After ten delays, Glenn finally entered his Friendship 7 space capsule on February 20, 1962. At 10 A. M., the Atlas rocket began to fire and lifted the spacecraft into the air. “We’re under way,” said Glenn.

The flight went smoothly at first. A problem did develop at one point, and Glenn turned off the automatic controls to fly the spacecraft manually for the rest of the trip. Glenn orbited the Earth three times, reporting on what he saw below. Live television coverage carried his words across the country. At one point Glenn said, “I don’t know what you can say about a day in which you have seen four beautiful sunsets.”

During the second orbit, a more seri­ous problem appeared. A warning light suggested that the capsule’s heat shield was loose. This piece on the bottom of the capsule was supposed to protect Glenn when the spacecraft reentered Earth’s atmosphere. If the shield did not remain in place, the capsule-and Glenn-would burn up.

A set of small rockets that sat under­neath the heat shield was supposed to be ejected before reentry began. NASA offi­cials decided to leave them on, hoping that they would help hold the shield in place. In the end, the shield was fine-it turned out the problem was actually with the warning light. Reentry was smooth, although hot, and Glenn’s craft splashed down in the Atlantic Ocean. Soon after, he was picked up by a U. S. Navy ship.

hang glider is a small, light­weight aircraft with no engine. It is controlled by a person who hangs, suspended in a harness, below a triangular wing. The pilot controls the hang glider with body movements and a control bar.

Hang Gliding History

The hang glider concept dates from the pioneer days of aviation at the end of the nineteenth century. German aviator Otto Lilienthal made glider flights, hanging underneath batlike wings that he built himself. His contraptions fitted
the definition of hang glider because Lilienthal controlled them by swinging his body from side to side. He launched himself by running down the slope of a hill. Once in the air, Lilienthal’s control of the glider was always less than com­plete. Although he made more than

2,0 successful glides, a fatal crash in 1896 ended the career of this brave and inventive aviator.

Other inventors saw that the hang glider could lead to larger and more controllable airplanes. Hang gliding
experiments led to the development of larger, person-carrying gliders and then to the first powered airplanes.

Glider, or sailplane, flying developed for sport and recreation during the twentieth century, but hang gliders were mostly forgotten until the 1970s. In that decade, enthusiasts started building them as a cheap, enjoyable way of fly­ing. Their enthusiasm was aided by the availability of lightweight metals, such as aluminum, to construct the frames. New, tough, plastic-based materials were ideal for the wing surfaces. Hang gliding started in the United States, and it soon became popular in other countries.

Today, hang gliding is a popular sport with people who cannot afford to buy or rent a full-size glider. Hang glid­ing equipment is simpler and less costly. These small, portable aircraft are also excellent for people who enjoy flying in places that are not suitable for launch­ing a conventional glider. One of the joys of hang gliding is that the pilot can take the glider almost anyplace flying is permitted. If conditions are suitable, the pilot can be up in the air within a few minutes of unloading the glider from a car trailer. A hang glider is collapsed and folded for transportation and stor­age when not in use.