Category FLIGHT and M ОТІOIM

Date of birth: July 18, 1921.

Place of birth: Cambridge, Ohio.

Major contributions: Pilot of first transcontinental flight to average super­sonic speed; first American to orbit Earth; oldest person to fly in space.

Awards: NASA Distinguished Service Medal; Congressional Space Medal of Honor.

John Glenn grew up in the small town of New Concord, Ohio. He became interested in science and aviation as a young boy. After graduat­ing from high school, Glenn studied at Muskingum College in his hometown and gained a degree in engineering.

Becoming a Pilot

In 1942, he joined the U. S. Navy and trained as a pilot. Glenn became an offi­
cer with the U. S. Marines in 1943. Soon after Glenn received his commission in the Marine Corps, he married Annie Castor, the childhood playmate who had become his girlfriend during high school and college.

During World War II, Glenn flew nearly sixty missions as a fighter pilot. After the war, he trained other pilots. When the Korean War broke out in 1950, Glenn volunteered for combat and flew nearly ninety more missions. In the two wars, he won six Distinguished Flying Crosses, along with several other mili­tary honors.

After the Korean War, Glenn became a test pilot. He gained national fame in 1957 by flying a plane from Los Angeles to New York City in less than 3/2 hours. That new speed record marked the first flight across the country with an average speed faster than the speed of sound.

Space probes sent across the solar sys­tem sometimes use the gravity of other planets to help them on their way. As a space probe flies toward a planet, the planet’s gravity pulls the probe and speeds it up. When it flies past the plan­et, gravity acts like a brake and slows it down again. If a planet stood still in space, this is all that would happen, and the probe would not gain or lose any speed. Planets do not stand still, how­ever, they move.

Jupiter flies around the Sun at about

30,0 miles per hour (about 48,000 kilometers per hour). If a space probe is flying in the same direction as Jupiter, it is swept along by the giant planet’s gravity. It speeds up by the amount of Jupiter’s speed, therefore gaining 30,000 miles per hour (48,000 kilometers per hour) without having to use any fuel. A planet’s gravity also can slow a probe

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GRAVITY ON OTHER PLANETS

PLANET GRAVITY

down or bend its flight path to steer it in a different direction. These maneuvers are called “gravity assist.”

Gravity assist enables a small space probe to visit distant planets without having to carry a huge amount of fuel. Space probes going to Mercury use Venus’s gravity to slow them down and set them on course for their destination. Space probes going to the outer planets use planets that they pass on the way to pick up the extra speed they need.

A planet has to be in the right place at the right time to give gravity assist to a space probe exactly when it is needed. For this reason, space probes often have to be launched within a certain period of time, called the launch window.

О Spanish astronaut Pedro Duque watches a water bubble float between himself and the camera on board the International Space Station. The bubble, like a lens, shows the astronaut’s miniature image.

The Hindenburg flew regular passenger services across the north Atlantic Ocean. The east-west trip from Frankfurt,

Germany, to Lakehurst, New Jersey, took 65 hours. Flying in the opposite direc­tion, from North America to Europe, took only 50 hours because of favorable tailwinds. During 1936, the Hindenburg made ten trips across the North Atlantic. The giant airship flew so well that engi­neers decided they could add ten extra passenger cabins, one with four beds, for the 1937 flights.

Passenger airship flights were usual­ly suspended for winter, because the craft flew at low altitude and at low speed and could be affected by bad weather. The Hindenburg’s first trip in

О The vast, complex frame of the Hindenburg fills a giant building during the airship’s construction in 1934.

1937 was scheduled for May, and on May 6, after crossing the Atlantic Ocean, it loomed into sight above Lakehurst, New Jersey. It was an impressive spec­tacle, and a crowd had gathered to watch the airship come in.

Astronauts living on the space station depend on the ISS life – support systems. There is no air in space and no water. Air and water must be transported from Earth or made inside the ISS.

The life-support system pro­vides the crew with oxygen and absorbs the carbon dioxide gas they exhale. The system also has to deal with other gases, such as ammonia, which are

By late 1903 the Wright brothers were ready to try out their invention. On December 14, 1903, Wilbur got ready for the first takeoff. The pilot did not have a seat-he lay stretched out on his front, slightly to the left of center. The engine started, the propellers whirled, but the Flyer refused to lift off the rail.

On December 17, they tried again, this time with Orville as the pilot. It was a cold, windy day. At 10:30 a. m., Orville released the wire that held the Flyer to the launch rail, while Wilbur held the right wing steady. The engine hummed, the propellers whirred once again, and the Flyer rolled slowly along the launch rail and then lifted into the air. At a height of only 10 feet (3 meters) or so, it flew for about 88 feet (27 meters) before swooping back to land safely. Five peo­ple witnessed the historic flight from a lifeboat station nearby.

The Flyer made three more flights that day. On the last flight, Wilbur flew for 853 feet (260 meters). Their longest flight that day lasted just under a minute. It was difficult to

О A replica of the first Flyer is on display at Kitty Hawk, North Carolina, in the Wright Brothers National Memorial visitor center.

О The Wright Brothers Memorial Tower was complete in 1932. It stands at Kitty Hawk on top of Kill Devil Hill. The inscription at its base reads: "In commemoration of the conquest of the air by the brothers Wilbur and Orville Wright-conceived by genius-achieved by dauntless resolution and unconquerable faith."

estimate speed, but the Flyer probably reached about 30 miles per hour (48 kilometers per hour). The Wrights sent a message home, packed up their airplane, and went off for dinner.

Flyer III

Because the Wrights had conducted their experiments away from spectators, their first flight did not create an immediate sensation. The world learned of the breakthrough, however, because the brothers built Flyer II and then the improved Flyer III, which they regarded as the first practical powered airplane.

Flyer III had a wingspan similar to the Flyer, but it was slightly longer and had a more powerful engine. Flyer III made its first flight on June 23, 1905. Between that date and October 16, 1905, the Wrights made nearly fifty flights, some lasting more than 30 minutes. They demonstrated that their airplane could turn, bank, and fly a figure eight pattern with perfect ease. On October 5, 1905, Flyer III flew for 24.2 miles (38.9 kilometers) in 38 minutes.

The brothers were ready to offer their machine for sale, with flying lessons. Wilbur Wright went to France to give demonstrations of flying, while Orville

continued to display the plane in the United States. In September 1908, Orville Wright completed fifty-seven cir­cuits of the drill field at Fort Myer, Virginia, managing to stay in the air for over an hour.

The original Flyer of 1903 was pre­sented to London’s Science Museum by Orville Wright in 1928, but it was returned to the United States in 1948. It is now in the National Air and Space Museum in Washington, D. C.

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SEE ALSO:

• Aerodynamics • Aeronautics

• Biplane • Glider • Lilienthal,

Otto • Propeller • Wind Tunnel

• Wright, Orville and Wilbur

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As high speeds became sought after, an aircraft’s shape became more important. Parts that stuck out into the air flowing around an aircraft had to be removed or smoothed out to reduce air resistance. The wooden struts and bracing wires between biplane wings had to go. Wood and fabric biplanes were replaced by all­metal monoplanes.

By the 1930s, nearly all new aircraft were monoplanes made from duralumin or similar aluminum alloys. Lots of new alloys with different properties were invented for building different parts of aircraft and spacecraft.

О The Boeing P-26A, nicknamed the "peashooter," was the first U. S. Army low-wing monoplane fighter constructed entirely of metal. This full-size peashooter was mounted for testing in a wind tunnel in 1934.

At first metal airplanes were built in exactly the same way as wooden planes. The structure was the same, and only the materials that were used were changed. The new materials made aircraft heavier, however, and a new type of structure was soon devised. Instead of building an airplane’s body from a strong, heavy, metal frame cov­ered with sheets of metal, a lot of the frame was removed. The thin metal skin itself provided some of the plane’s strength. This is called a stressed-skin structure. To make sure the thin skin did not bend or buckle, it had to be fastened securely to the frame with thousands of metal fasteners called rivets.

Mitchell’s work met resistance, however. Senior officers were not yet willing to accept the idea that air power would be important. They were outraged at Mitchell’s charge that battleships had become outdated. At that time, U. S.

battleships were the largest and most powerful ships in any navy. Naval offi­cers insisted that the defense of the United States depended on a fleet of these ships to block any invasion of the nation.

Mitchell countered that the ships could easily be destroyed by air. He campaigned in the press for the right to test his theories. He suggested a simulat­ed attack on a German battleship seized at the end of World War I. In June and July 1921, Mitchell got his chance. In tests, as he had predicted, aircrews sank several ships, including four battleships. “No surface vessels can exist wherever air forces acting from land bases are able to attack them,” Mitchell wrote.

Although proven correct, Mitchell remained unpopular in military circles. He continued to use the press to accuse senior military officers of ignoring air defenses. He toured U. S. naval bases in the Pacific Ocean and issued a stark warning: “If our warships [at Pearl Harbor, Hawaii] were to be found bottled up in a surprise attack from the air and our airplanes destroyed on the ground. . . it would break our backs. The same prediction applies to the Philippines.”

Mitchell’s words proved uncannily accurate years later, when the Japanese severely damaged U. S. ships and grounded airplanes with the 1941 attack on Pearl Harbor from the air.

C In one of Billy Mitchell’s tests to prove the value of air power, an MB-2 aircraft successfully blew up an obsolete battleship in 1921.

Court-Martial

In early 1925, Mitchell’s appointment in the U. S. Air Service expired. Instead of renewing it, army commanders sent him to an isolated military base in Texas. Later that year, the navy suffered two air disasters when a seaplane broke down and a dirigible exploded. Mitchell immediately released a stinging attack on the heads of the navy and the army, accusing them of “almost treasonable negligence of our national defense.”

His superiors had had enough, and they convened a court-martial. Mitchell was charged with insubordination (not obeying senior officers). After a seven – week trial he was found guilty. The ver­dict was suspension from duty for five years, but Mitchell decided to resign from the U. S. Army altogether.

Mitchell spent his remaining years writing and speaking to promote the ideas he had long advanced. He became ill in the mid-1930s and died at the age of fifty-six. During World War II, Mitchell’s basic argument was proven true. Air power proved vital to Allied victory in both Europe and the Pacific.

In April 1942, a few months after the attack on Pearl Harbor, U. S. bombers attacked Japan using B-25s, nicknamed “Mitchells.”

In 1946, ten years after his death, the U. S. Congress voted to award Mitchell a Congressional Medal of Honor, in trib­ute to foresight.

SEE ALSO:

• Aircraft, Military • Curtiss, Glenn

• World War I • World War II

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avigation is the steering or directing of a course. Migrating birds, animals, and even insects seem able to navigate across the world with ease. People have developed ways of using nature, science, and technology to do the same thing—to figure out their position and find their way across land, sea, sky, and even in space.

Following Instinct and Landmarks

Monarch butterflies fly more than 1,500 miles (2,400 kilometers) on their annual migration across North America. One seabird, the Arctic tern, makes the longest migration journeys of any living creature. Every year, it flies up to 22,000 miles (35,400 kilometers) between the Arctic and Antarctic. Some animals are born with an instinct for migrating in a particular direction. Birds may navigate by recognizing familiar landmarks such as rivers and mountains. They also may use the position of the Sun and stars. Yet others seem to be able to sense the Earth’s magnetism, as if they have a nat­ural compass that directs them.

The first pilots relied on navigation methods similar to those used by birds. Planes flew low so that pilots could nav­igate visually by following landmarks such as roads, rivers, and railroads. For longer flights and for flights over oceans, a method called dead reckoning was used. A pilot used a map to figure out which direction to fly and then

measured the distance to the destination. Knowing how fast a plane flew, a pilot could figure out the journey time. If the plane was flown in the right direction (using a compass) at the correct average speed for the calculated length of time, it should arrive at its destination. In the real world however, an aircraft could be blown off course by wind, so pilots had to allow for this when plotting their course. Today, pilots of small aircraft still can navigate using dead reckoning and by looking out for landmarks.

THE STARDUST MYSTERY,

In 1947, an airliner called Stardust was flying from Buenos Aires, Argentina, across the Andes moun­tain range to Santiago, Chile. Just before it was due to land, it van­ished. Searchers found nothing. In 2000, the wreckage was found, and an explanation to the old mystery was pieced together. Because of bad weather, the airliner had flown so high that it reached the high-speed air current of the jet stream and was flying against it. The crew’s naviga­tion calculations indicated that they had crossed the mountains, but the jet stream had slowed them down so much that they were still over the mountains. Thick clouds prevented them from seeing the ground. As they descended to land, the plane crashed into a mountainside and fell onto a glacier, a slow-moving river of ice. The wreck was soon covered with snow and then sank into the glacier. It took fifty-three years for the wreckage to travel downhill inside the glacier and appear at the bottom.

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Professional pilots must have an instru­ment rating. For this, they need to do at least 50 hours of cross-country flying (between one airfield and another). They must be able to fly by visual flight rules (VFR) and instrument flight rules (IFR) using electronic aids. IFR involves instrument training, during which pilots fly using just their instruments so that they will be able to fly even when visi­bility is poor or zero. Commercial pilots also familiarize themselves with the use
of radio, radar, and the landing systems used at airports, such as the microwave landing system (MLS) and the older instrument landing system (ILS).

Before gaining a commercial pilot license (CPL), a pilot must have complet­ed at least 250 hours of flight time, recorded in a personal log book, and must have learned to fly more complex aircraft (with flaps and retractable land­ing gear). The flight examination includes two flight sessions: one in a training aircraft and another in a more complex airplane, although a student may fly the entire test in the complex airplane. Many commercial pilots add a multi-engine rating, which they need to fly aircraft with more than one engine.

The basic principle of radar is very sim­ple. It sends out radio waves and then picks up any waves that are reflected back. Most radar systems are more com­plex, however, and they can tell much more about an object than just the fact that it is there. They can show its loca­tion, bearing (direction), range (dis­tance), velocity, and altitude.

A radar system has four main parts. A transmitter produces radar signals.

An antenna sends signals in the form of electromagnetic waves and picks up any reflections that return. A receiver ampli­fies the weak radar reflections and ana­lyzes them. A display shows the received information on a screen.

Radar uses short radio waves called microwaves. The simplest type of radar is pulse radar. It sends out short bursts, or pulses, of radio waves and listens for any reflections that bounce back from a target, such as an aircraft. The direction from which the reflection comes shows the aircraft’s bearing. The time the pulse takes to bounce back gives its range.

Antennae

A dish-shaped antenna can be steered to scan a particular area of the sky. It may swing back and forth, or it may rotate so that it scans the whole sky in all direc­tions. The most modern radar systems use a flat antenna that stays fixed in one place. A flat antenna is constructed from

О A simple radar has an antenna that sends out signals in the form of pulses of radio waves. It picks up any echo pulses that come back and uses them to measure an object’s distance and movement.

DOPPLER RADAR

When a police car races past sound­ing its siren, the sound rises in pitch as the car approaches and falls as it goes away. This is called the Doppler effect, and it happens with all kinds of waves, including microwaves. Radar equipment can be designed to make use of this effect. It can show if something is flying toward the radar antenna or away from it, and how fast. A type of radar called Doppler radar was developed in the 1960s. It uses continuous radar waves instead of pulses. Pulse – Doppler radar systems combine basic pulse radar systems with Doppler radar.

At first, Doppler radar was used mainly for weather forecasting. By the 1980s, Doppler weather radars were able to measure the speed and direction of raindrops inside clouds and storms. Portable Doppler radars carried on the back of trucks are used to study the most extreme weather systems, especially thun­derstorms and tornadoes.

thousands of small, electronic transmit – and-receive modules, and the radar beam is steered electronically. These radars are called electronically scanned arrays, or phased arrays. They can scan far faster than a rotating dish antenna, they can track many more targets, and – with fewer moving parts-they are more reliable.

Advanced combat aircraft, such as the F-22, are equipped with electronically scanned array radar. They can locate and track multiple high-speed targets and pass on the target information to the air­craft’s weapons systems.