Category FLIGHT and M ОТІOIM

Satellites vary in size from a few pounds to many tons. Some remain in orbit for only a few weeks, while others have an expected lifetime of hundreds of years. They are packed with scientific instru­ments, usually miniaturized to save weight and space. Manufacturing is closely monitored and takes place in germ-free conditions. All systems are thoroughly tested-once launched, satel­lites must continue to work under remote control for long periods of time.

SATELLITE LAUNCHERS

A satellite can be carried into space in the cargo bay of a Space Shuttle, or it may be blasted into space on top of a multistage rocket or launch vehicle. An expendable launch vehicle, or ELV, is used only once. An ELV has two or more booster stages; each stage falls away when its engine burn is completed. The final stage sends the pay­load (the satellite) into orbit.

The launch vehicle Pegasus is itself launched from beneath a converted Lockheed L-1011 aircraft. The launcher can place a satellite weighing up to 970 pounds (440 kilograms) into near-Earth orbit. Pegasus launched the Solar Radiation and Climate Explorer and the Galaxy Evolution Explorer satellites in 2003.

A larger satellite, or a satellite intended for high orbit, requires a more powerful launcher, such as a ground-launched Athena or Delta rocket. Delta rockets have launched many satel­lites since the 1960s, including TIROS, Nimbus, ITOS, and Landsat satellites. The big Delta IV can launch a payload of 50,800 pounds (23,070 kilo­grams) into low-Earth orbit.

O A huge Delta IV rocket stands at Cape Canaveral, ready to carry an observation satellite

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Most satellites are fitted with panels of solar cells that convert energy from sunlight into electricity. They use solar energy to power instruments and the communication systems that send data, such as video images, back to Earth.

A satellite is directed by remote con­trol from mission centers on the ground,
where scientists monitor its orbit, send instructions, and receive data from the satellite’s instruments. Under command from Earth, a satellite can be shifted in orbit by firing small thruster rockets.

A satellite may be in constant com­munication with mission control. If it is in a low orbit, it may be contacted only

when it passes overhead. Each pass may last just 10 minutes, but the satellite may fly by ten or twelve times a day, depend­ing on its orbit. Some satellites are visi­ble at night as they pass overhead.

A satellite that has malfunctioned, or has come to the end of its operational life, is normally shut down and then allowed to burn up as it reenters the atmosphere. Some defective satellites, however, have been picked up by Space Shuttle astronauts for repair.

Skydivers usually jump from an air­plane, although they also may leap from helicopters and balloons at various heights. A typical jump height is between 10,000 and 13,000 feet (3,050 and 3,960 meters). On August 16, 1960, Captain Joseph Kittinger of the U. S. Air Force stepped out of a balloon over New Mexico at a height of 102,200 feet (31,150 meters). He experienced a record-breaking free fall, skydiving for 4 minutes and 38 seconds before he opened his parachute at 17,500 feet (5,330 meters).

In free fall, a skydiver does not feel a falling sensation, even though speed through the air may reach 120 miles per hour (193 kilometers per hour). Skydivers do not experience the discom­fort of acceleration. During the descent, they may perform such maneuvers as turns, front and back loops, barrel rolls, and joining up with other skydivers in formations. There is a deceleration sensation when the parachute opens,

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О Members of a women’s skydiving team descend after opening their parafoils. Use of the parafoil has increased distance and maneuvering ability for skydivers.

slowing the descent to about 12 miles per hour (19 kilometers per hour).

The Parachutes

To end a dive, the skydiver first pulls out a pilot parachute. Measuring about 3 feet (0.9 meters), the pilot parachute is stored in a pocket on the harness, or rig. As this small parachute inflates in the wind, a cord known as the bridle operates the release mechanism for the main parachute and its lines. A rectan­gle of fabric (the slider) separates the

THE PARAFOIL

The invention in the 1960s of the wing parachute, or parafoil, revolutionized sports parachuting. The modern para­chute, known as a ram air wing, flies almost like a paraglider. The canopy contains seven to nine panels, or cells, open at the front so that air can enter.

The parachutist can alter the amount of air inside the canopy by twisting a handgrip. By tugging on the steering lines, the parachutist can make turns and steer toward a landing site.

parachute lines into four groups and works its way down until the canopy is fully open and the slider is just above the skydiver’s head.

A skydiver carries two full-size para­chutes, one of which is kept in reserve. The minimum safe height for opening a parachute is around 2,000 feet (610 meters). This height gives sufficient time for the skydiver to open the reserve parachute if the main parachute fails to function. Many skydivers carry an automatic activation device (AAD), which opens the reserve parachute at a safe altitude if the skydiver fails to open the main parachute. Skydivers always carry an altimeter so they know at what height to open the parachute. If the main parachute malfunctions after it has been opened, the skydiver uses one handle to discard it and pulls another

handle (on the parachutist’s chest) to open the reserve parachute.

Rectangular canopies are better than traditional round canopies for competition jumping as they are much easier to steer. A rectangular canopy will not collapse should another parachutist fly beneath it and take its air. Using these modern canopies, skydivers can fly in stacks, one above the other. An experienced skydiver with a modern parachute can fly cross-country for as much as 10 miles (16 kilometers), reach­ing speeds of up to 30 miles per hour (48 kilometers per hour) over the ground. He or she can perform dramatic maneuvers such as the swoop: a fast, downward approach before leveling off just above the ground.

eronautics is the science of building and flying aircraft. The term covers scientific study, design, and technology. It also includes the manufacture and operation of all types of aircraft, both lighter than air (such as airships) and heavier than air (such as airplanes).

Aeronautics involves a great variety of scientific and engineering disciplines. Aerodynamics and propulsion are important in aeronautics. So are materi­als, structures, control systems, and computing.

Energy from the Sun passes through the atmosphere’s layers to warm Earth’s sur­face. The surface then warms the atmos­phere. The warm air rises and draws in more air underneath to replace it. These air currents caused by the Sun and also by the spinning motion of Earth are responsible for the weather.

Some gases in the atmosphere are very good at soaking up warmth instead of letting it escape into space. These gases make the atmosphere warmer overall. The rise in temperature caused by these gases trapping heat is called the greenhouse effect, and the gases that trap the heat are known as greenhouse gases. Water vapor, carbon dioxide, and methane trap the most heat.

Without the greenhouse effect, the world would be about 60°F (33°C) cold­er than it is now. The world is gradually warming up, however, in a process called global warming. Many scientists believe this is happening because of the increase in greenhouse gases produced
by human activities. When fossil fuels such as coal and oil are burned, they release carbon dioxide, which traps heat.

Depending on how much the atmos­phere warms up, global warming could cause droughts in some parts of the world, floods in other parts, and more

BLUE SKIES AND RED SUNSETS

Air is colorless, so why is a clear sky blue? Sunlight contains all the colors of the rainbow mixed together. As sunlight streams through the atmosphere, it hits air molecules. The molecules scatter the light in all directions, but the blue part of the light is scattered more than the other colors, because its wavelengths are shorter. The sky, therefore, looks blue in every direction.

Brilliant red sunsets are also caused by light scattering. When the Sun is low in the sky just before it sets, sunlight travels more than thirty times farther through the atmosphere to reach the eyes of an observer than it does when the Sun is high in the sky. Most of the blue part of the sunlight is scattered out, leaving the red and orange parts of the light (with their longer wavelengths) to give the sunset those colors.

violent storms everywhere. If a warmer atmosphere melts the polar ice caps, the sea level could rise enough to flood coastal cities. Crops could fail in some places as the climate changes. Many people believe the effects of global warming are already being seen.

The introduction of jet planes brought about a revolution in passenger flying. The De Havilland Comet first flew in 1949 and went into service in 1952. It was followed by the Boeing 707, which could fly at 580 miles per hour (933 kilometers per hour) at 40,000 feet (12,190 meters). When the 707 entered service in 1958, critics argued that no airline would be able to fill its 130 seats. By 1969, however, the Boeing 747 was offering seats for 350 passengers.

Turboprop airliners, such as the Vickers Viscount and Lockheed Electra, proved briefly popular. Turboprop planes have gas turbine engines that turn propellers. They were slower than jets, but they were quiet and efficient. These aircraft were soon replaced, how­ever, by new medium-size jets.

The commercial aerospace industry of the late twentieth century had to

PRESSURIZED CABINS

The air is very thin at high altitudes, and early pilots flying above 10,000 feet (3,050 meters) would have needed oxy­gen tanks to breathe. A better system, introduced during World War II, was the pressurized cabin. Pressurized cabins were first used commercially in 1940, in the Boeing 307. After the war, pressur­ized cabins became standard on aircraft carrying passengers.

Commercial aircraft fly between 30,000 and 40,000 feet (9,150 meters to 12,200 meters). Whatever the temper­ature and altitude may be outside, the compressed air inside a pressurized cabin allows people to function as they would at lower altitudes. The pressurized air gives passengers enough oxygen to breathe comfortably. The introduced air system also maintains a comfortable temperature.

The pressurized air, which comes from compressors in the aircraft engines, flows through the wings to air condi­tioning units under the floor of the cabin.

It is mixed with filtered air already in the cabin (the filters trap any microbes) and is circulated in a continuous flow that dilutes odors and regulates temperature.

The air in the cabin changes every two to three minutes. In spite of the general belief that airplane air is full of recycled germs, airline passengers breathe cleaner air than most office workers.

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anticipate public demand for the future. Did passengers want cheaper fares in bigger aircraft, like the Boeing 747 and Airbus 380? Or would they pay more for the high-speed flights offered by the supersonic Concorde? The 747 won the commercial battle easily. Boeing 747s are still being built, while Concorde was retired in 2003. Only sixteen Concorde planes were ever flown commercially.

By 2000 Boeing aircraft had come to dominate the global market in com­mercial aviation. Boeing’s main rival is the European consortium Airbus Industries, a group of aerospace compa­nies that makes the Airbus family of commercial jets.

very part of an aircraft has been carefully designed by one or more aircraft designers. The materials used and the shapes of aircraft have changed over the years, but the impor­tance of design remains the same.

Four Aspects of Aircraft Design

There are four main subjects an aircraft designer must understand before an air­craft can be designed: aerodynamics, propulsion, materials and structures, and stability and control.

Aerodynamics is the scientific study of how air flows around an airplane. Propulsion is all about engines, which provide the thrust to move an airplane through the air. Materials and structures
cover what an airplane is made from and how it is built. Stability and control are concerned with how an aircraft flies and how its flight is controlled.

The shape and size of an aircraft depend on what it is designed to do. In other words, form follows function. Airliners have to be big enough to carry a certain number of passengers and their luggage. Fighter planes have to be small, highly maneuverable, and well armed. Cargo planes have to be large and pow­erful enough to carry huge weights of cargo, and they need big doors for load­ing and unloading their cargo easily.

Some use of airships has continued. Graf Zeppelin was briefly used during World War II by the Germans, but it was scrapped in 1940. The U. S. Navy contin­ued to use airships into the 1960s. In 1960 one of its airships flew for 95 hours and 30 minutes without landing or refueling once.

Today, airships are flown mostly for fun or for publicity and media work. There is growing interest, however, in new kinds of airships using modern technology. With modern materials and helium gas, a new generation of airships would be safe, efficient, and able to carry cargo and passengers for very long distances. Cruising at low level, an airship can provide spectacular views for passengers more interested in scenery than fast flight times.

Airships are also environmentally friendly. They use less fuel than air­planes, and they are quiet. Airships do not require airports with runways. Their main disadvantage is their slow speed. Hindenburg (the fastest airship) had a top speed of only 84 miles per hour (135 kilometers per hour). The largest airship currently flying, Spirit of Dubai, a Skyship 600 design, is limited to 50 miles an hour (80 kilometers an hour). Another disadvantage is that airships cannot fly high enough to cross the highest mountain ranges, such as the Rocky Mountains in North America or the Himalayas in Asia.

Current interest in airships focuses on their potential use as floating telecommunications centers or as trans­portation for heavy cargo. A German airship project called CargoLifter pro­poses to carry payloads of about 165 tons (150 metric tons) at a height of 6,560 feet (2,000 meters) for several thousand miles. About the same size as the Graf Zeppelin and Hindenburg, this modern airship can carry three times the payload of those earlier aircraft, because it is much lighter when unloaded. The CargoLifter is semi-rigid, and, instead of a heavy metal frame like a Zeppelin’s, it has a strong lengthwise keel, like a ship. The keel holds the cargo bay, flight deck, crew quarters, and engines.

Aircraft designers are also working on hybrid craft that combine airship and airplane. Such aircraft would need a takeoff run to get airborne, like most airplanes. They would also generate some lift from their shape as well as from the gas inside them. For maximum lift, a hybrid airship would have an effi­cient aerodynamic shape, such as a disk or an aerofoil (flying wing). The airship of the future might well look like the flying saucer of science fiction.

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SEE ALSO:

• Aerodynamics • Balloon • Future of Aviation • Hindenburg

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Date of birth: August 5, 1930.

Place of birth: Wapakoneta, Ohio.

Major contributions: First person to pilot the docking of two space vehicles; first person to set foot on the Moon. Awards: Presidential Medal of Freedom; Congressional Space Medal of Honor; NASA Distinguished Service Medal; Royal Geographic Society Gold Medal; Federation Aeronautique Internationale Gold Space Medal; and many more honors, awards, and honorary degrees.

orn on a farm in rural Ohio, Neil Armstrong took his first airplane flight at age six. He quickly became interested in aviation. Armstrong spent many hours of his childhood building model planes and reading books about flying. He started flying lessons at age fourteen and earned his pilot’s license two years later.

After graduating from high school, Armstrong began studying aeronauti­cal engineering at Purdue University in Indiana. He interrupted his studies to serve in the U. S. Navy from 1949 to 1952. During that time Armstrong flew as a fighter pilot in the Korean War and earned two Gold Stars. After his service in the Navy ended, Armstrong became a civilian again. He graduated from Purdue and became a test pilot for the government. From 1955 to 1962, Armstrong flew more than 1,100 hours, testing many different kinds of aircraft.

In September 1962, Armstrong joined the National Aeronautical and Space Administration (NASA) as an astronaut. He was one of the few civilian astro­nauts. In 1966 Armstrong made history on his first space mission, Gemini 8, when he became the first person to maneuver one spacecraft to dock with another in space.

Early in 1969, Armstrong was named as commander and pilot of the Apollo 11 mission that aimed to take the first peo­ple to the Moon. Also on the crew were Buzz Aldrin and Michael Collins, both experienced astronauts.

On July 16, 1969, the trio blasted off from Florida. A few days later, they

entered orbit around the Moon. Armstrong and Aldrin climbed into the lunar landing craft, the Eagle. Collins remained in orbit aboard the command module, Columbia. The two craft sepa­rated, and Aldrin piloted the Eagle down to the Moon’s surface. Shortly after 4:00 p. m. on July 20, the landing craft touched down. Armstrong announced by radio, “The Eagle has landed.”

For the next six and a half hours, the two astronauts prepared for their his­toric walk on the Moon’s surface. Just before 11:00 p. m., Armstrong stepped down the ladder onto the Moon’s sur­face. As he did so, he said, “That’s one small step for man, one giant leap for mankind.” A camera on the side of the spacecraft displayed the historic step to millions of people around the world watching on television.

Armstrong and Aldrin took some rock samples, set up some experiments, and placed a U. S. flag on the Moon. Fired by rockets, the ascent stage of the lunar module took the astronauts safely back to the Columbia on July 21. The next day, they began the return trip to

О Most of the photos from the Apollo 11 mis­sion were of Buzz Aldrin taken by Neil Armstrong. This is one of the few clear photographs of Armstrong, showing him next to the modular equipment storage assembly of the Eagle.

Earth. Columbia splashed down in the Pacific Ocean on July 24.

Officials worried that the astronauts might bring back some unknown space germs with them. Armstrong, Aldrin, and Collins were held in isolation for more than two weeks. When finally released, they were celebrated in cities across the United States and in many countries around the world.

From 1970 to 1971, Armstrong served NASA in an administrative job. He then resigned and became a professor of aerospace engineering at the University of Cincinnati in Ohio until 1979. Later Armstrong worked for companies in the aerospace industry. Armstrong also helped lead the commission that investi­gated the fatal loss of the Space Shuttle Challenger shortly after takeoff on January 28, 1986.

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SEE ALSO:

• Apollo Program • Astronaut

• Challenger and Columbia • NASA

• Spaceflight

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In a hot air balloon, the heat comes from a propane gas burner. The pilot turns on the burner to send hot air into the balloon. The balloon is made of a tough, nonflammable material such as nylon

BALLOON JUMP

The world’s longest delayed-drop parachute jump was made from a balloon. On August 16, 1960, Captain Joe W. Kittinger jumped out of a balloon 102,800 feet (31,333 meters) above New Mexico. He fell 84,700 feet (25,817 meters) before his para­chute opened. In 1984, Kittinger became the first person to fly the Atlantic Ocean alone in a balloon.

He flew from Maine to Italy in about 86 hours.

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or polyester. The bigger the bag, the more weight (payload) the balloon can lift. Passengers ride in a basket or similar structure hanging beneath the balloon. To descend for landing, the pilot releases air from the top of the balloon. Hot air balloons are popular with sports balloonists.

Gas balloons are usually filled with helium. This gas is safer than hydrogen because it does not catch fire. Gas bal­loons have more lifting power than hot air balloons. They can also go higher and stay aloft longer.

The largest type of gas balloon is a superpressure balloon. The pressure of gas inside the bag is higher than the pressure of the outside air. At launch, a superpressure balloon is only partly filled with gas. As the balloon rises, the gas expands and fills the bag. The

largest such balloons have a volume of more than 70 million cubic feet (2 mil­lion cubic meters), and they are unmanned aircraft.

Today, scientists find unmanned gas balloons useful for studying the weather and the upper atmosphere. Weather bal­loons carry radiosondes—instruments that measure temperature, humidity, and air pressure—which send back data by radio.

There are two kinds of bird flight: flapping and gliding. During flapping flight, the bird beats its wings up and down. The large primary feathers in the wing do most of the propulsion; the smaller secondary feath­ers help to maintain lift. The wings move in two directions while flapping: up and down and in a circular or figure 8 move­ment. The wingtips move faster and farther than the rest of the wings. The smaller the bird, the faster its wings flap.

The downbeat is the power stroke. On the downbeat, the wing feathers overlap closely so that air cannot pass through them but is instead pushed downward. The wing moves downward and forward. The primary feathers are bent back at their tips so the wing performs like a
propeller, pulling the bird forward. Power is produced on the upbeat, too, although less so than on the downbeat. As the wing moves upward, the primary feathers are bent back and move apart a little, fanning open to allow air to slip through the gaps between them. This reduces wind resistance and saves energy.

THE SPEED OF BIRDS

Peregrine falcon: 200 miles per hour (320 kilometers per hour) in a dive.

Spinetailed swift: 105 miles per hour (170 kilometers per hour). Canvasback duck: 65 miles per hour (105 kilometers per hour).

Pigeon: 60 miles per hour (96 kilometers per hour).

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