Category FLIGHT and M ОТІOIM

Space engineers are now interested in developing cheaper launch systems for satellites and space tourists. One possi­bility is a space elevator. This idea, basi­cally a giant tower reaching into space, was first put forward by the Russian sci­entist Konstantin Tsiolkovsky at the beginning of the twentieth century. It was later described by the science fiction writer, Arthur C. Clarke. The space eleva­tor would consist of a tower, some 31 miles (50 kilometers) high, with a cable

C NASA’s Advanced Projects Office has put together plans for a space elevator, an idea that has previously been explored only in science fiction.

linking the top of the tower to an orbital space station. Passengers and cargo pay­loads would be transported into space along magnetic tracks fixed to the cable, riding in magnetically levitated (or maglev) vehicles.

Away from the billion-dollar nation­al and international space programs, individuals are planning space tourism in privately sponsored spacecraft. The pioneer in this field of spaceflight was SpaceShipOne, first flown in June 2004.

Such opportunities will increase the popularity of space tourism.

GPS was originally intended only for military use, but a civilian service was added. The civilian service was less pre­cise-in fact, errors were deliberately included to make it even less accurate so that enemy military forces could not make use of it. The civilian service offered what was called Selective

О GPS is used aboard military aircraft for pin­pointing targets to be destroyed. Soldiers in the field use handheld survival radios equipped with GPS for search and rescue missions.

О The GPS IIR satellites were designed to last longer and be more accurate than earlier GPS equipment. GPS technology is constantly improving.

Availability, a system that enabled receivers to calculate their position only to within about 300 feet (100 meters). In 2000, President Bill Clinton ordered the Selective Availability system to be turned off. The accuracy of the civilian GPS service was immediately improved.

Most receivers are now designed to provide extra features. If they are in a moving vehicle, such as an aircraft, they compare a series of positions and use them to calculate the vehicle’s speed and direction. If this information is com­bined with a digital map, GPS can be used for navigation. Professional map – makers and surveyors also use GPS to produce very accurate maps. Farmers even may use GPS to map their fields and calculate how much fertilizer or weed killer is needed in different places.

The single-rotor helicopter has one large rotor, usually mounted toward the front of the body and above the passenger compartment. A smaller rotor is attached to the tail of the helicopter.

The main rotor may have between two and eight blades. The tail rotor can have two, twelve, or more blades. It is mount­ed vertically on the side of the tail and is therefore at right angles to the main rotor. The tail rotor provides stability, acting against the tendency of the heli­copter to spin around in the opposite direction of the main rotor blades. This spin force is known as torque.

The tail rotor may be shrouded, or enclosed in a cover-it is then called a fenestron. This is quieter and safer, but less efficient. A tail rotor can use up to 5 percent of the engine’s power without helping the helicopter fly upward or for­ward. One way of improving efficiency is to angle the vertical stabilizer so that it counteracts the torque without taking power from the engine. Helicopter pilots call this “slipstreaming.”

For their size, many insects fly extreme­ly quickly. Most insect flights are short hops during food-gathering expeditions. Honeybees, for example, buzz from flower to flower, using a complex navi­gation system to find their way between the nest or hive and the flowers. They have a system of body language to tell other bees where to find the flowers. Flying is energetic, and few insects can sustain such a high output of energy for long. A honeybee usually flies for up to 15 minutes before it has to feed and refuel its muscles.

A few insects make long migratory flights. The North American monarch butterfly is a good example. It flies south in large groups to escape the northern winter, returning the following year. Migrating butterflies can fly for 100 miles (160 kilometers) without stopping for food. Another long-distance flier, though an unwelcome one, is the desert locust of Africa and Asia. A swarm of locusts may contain billions of insects. Locusts can fly hundreds of miles with­out feeding before they finally land and ravenously eat every blade of grass or clear fields of their crops.

FAST WINGS

The fastest flying insects are dragon­flies. Over a short distance, they have a top speed of about 60 miles (96 kilometers) per hour. The fastest wing beat ever recorded for an insect was that of a tiny midge: nearly

65,0 beats per minute. Most insects are much slower. A housefly beats its wings about 200 times every second-a mere 12,000 times a minute! Butterflies have the slowest wing beats of any insect, at around 500 times a minute.

After World War II, U. S. scientists began rocket experiments at the White Sands military facility in New Mexico. As the United States developed its missile program, a new launch site was needed. In 1949, President Harry S. Truman

authorized a firing range at Cape Canaveral in Florida.

The area was thinly populat­ed and therefore an ideal site for testing secret and some­times unpredictable rockets.

Cape Canaveral also offered a fine, clear climate and access to thousands of square miles of the Atlantic Ocean.

Cape Canaveral attracted more media and popular interest after the United States launched its first satel­lites, Vanguard and Explorer, in 1957 and 1958. Despite these successes, U. S. public opinion was critical because the Soviet Union had taken the lead in the “space race.”

The demand for more action led to the formation of NASA in October 1958, and Cape Canaveral became a major launch base for NASA as well as for the U. S. military.

The United States in Space U. S. space exploration opened a new chapter in May 1961, when President John F. Kennedy announced the United States would send astronauts to the Moon before the end of the 1960s. On July 1, 1962, Cape Canaveral became NASA’s new Launch Operations Center. The first director of the center was Dr. Kurt H. Debus, a rocket scientist. The Launch Operations Center was renamed the John F. Kennedy Space Center in December 1963, a month after the pres­
ident’s assassination. (Cape Canaveral was renamed Cape Kennedy that year, but it reverted to its old name in 1973.)

The Apollo Program was now under­way. So vast was this project, and so big was the three-stage rocket planned to launch Apollo spacecraft to the Moon, that NASA decided to build a larger launch facility. Several sites-including ones in Hawaii, Texas, California, and the Caribbean-were considered before NASA and the Department of Defense chose Merritt Island, west of Cape

Apollo Moon missions, a huge con­struction program was undertaken with the help of the U. S. Army Corps of Engineers. A new launch center, named Launch Complex 39 (LC-39), included the vast Vehicle Assembly Building (VAB).

With the Mercury and Gemini spaceflights of the 1960s, interest in spaceflight grew. Each blastoff attract­ed excited media coverage. Kennedy Space Center became the center of world attention in 1969, when the Apollo 11 mission blasted off from LC-39 for its historic trip to the Moon, honoring President Kennedy’s pledge.

Lindbergh dreamed of winning the Orteig Prize, a $25,000 award promised to the first pilot to fly nonstop across the Atlantic Ocean between New York and France. In 1926, a new engine became available-the Wright Whirlwind. It seemed powerful enough to carry an air­craft that long distance.

Lindbergh convinced his employers at Robertson Aircraft Company to let him pursue the prize. He found business­men in St. Louis willing to provide the money he needed to buy a plane. He was

О The Spirit of St. Louis was photographed during flight in 1927.

unable to make a deal with one of the famous aircraft companies, so he contacted a small firm, Ryan Airlines, in San Diego, California.

Ryan agreed to build him a plane for $10,000 and promised to meet Lindbergh’s two-month deadline.

Starting in late February 1927, Lindbergh worked closely with Ryan’s mechanics to build his airplane. He wanted to have a single engine and a single crew member—himself. That way, the plane could be as small and light as possible. He took every step possible to shed weight, dropping a radio to save 90 pounds (41 kilograms) and doing with­out fuel gauges to save a few more.

On April 28, 1927, the airplane was completed. Lindbergh named it the Spirit of St. Louis in tribute to his finan­cial backers. After testing the plane, he pronounced it ready.

Most missiles are powered by rockets, but the cruise missile is powered by a small jet engine and is not ballistic. The missiles have wings, and they fly like planes without a pilot. Cruise missiles guide themselves to the target, flying low to avoid enemy radar. They are very accurate indeed: a cruise missile can fly 700 miles (1,126 kilometers) and then hit a designated target the size of a car.

A cruise missile can be fired from a launcher on the back of a truck, or from an airplane, a ship, or even a submerged submarine. A small rocket launches the missile, and then the rocket falls away and the missile’s jet engine takes over. Cruise missiles dropped from aircraft do not need booster rockets, because they are already traveling fast enough when they are launched. The tailfins and wings spring out from the missile’s body as it begins to fly toward its target.

The cruise missile is steered by a system called inertial guidance. The system measures how far the missile has traveled, and in which direction, from the place where it was launched. Inertial guidance is not perfect, and small errors can build up during a long flight and push the missile off course. The missile checks its position with a radar system called TERCOM (short for terrain

О An MIM-104 Patriot missile is fired into the sky. Patriot launch tubes, mounted on the backs of trucks, are deployed in conflict zones, such as Iraq and Afghanistan.

contour mapping). This system looks at the ground below it and compares the shape of the ground to a map stored in its memory. Any error found by TERCOM is used to correct the missile’s course. The latest cruise missiles also use GPS (Global Positioning System) to make sure that they stay on course.

As the cruise missile closes in on its target, it switches to a different guidance system. This uses a camera in the mis­sile’s nose to look at the view ahead and compare it to an image of the target stored in its memory. When it spots the target, it flies straight toward it.

NASA quickly captured the public imagination with Project Mercury. Amid a blaze of publicity, seven pilots (all men) were chosen to be America’s first astronauts. Alan B. Shepard was the first American to fly into space on May 5, 1961, squeezed inside a cramped Mercury capsule launched by a Redstone rocket. On February 20, 1962, John H. Glenn, became the first U. S. astronaut to orbit Earth.

As the Mercury program contin­ued, NASA scientists also were engaged in a range of unmanned space activities-sending probes to the Moon and to Mars, for example. Public attention, however, focused on the “space race” between the Soviet Union and the United States. The declared U. S. intention, as stat­ed in May 1961 by President John F. Kennedy, was to land men on the Moon and bring them back safely. This was an immense challenge, and many people doubted NASA could achieve the president’s goal.

After the completion of the Mercury program, NASA pro­gressed to two-person flights in Earth’s orbit, using the larger Gemini spacecraft. Gemini flights provided valuable experience in space piloting, rendezvous and docking, extra-vehicular activity (space walks), and reentry and splashdown techniques.

О President John F. Kennedy (center, facing right and wearing sunglasses) toured NASA’s facilities at Cape Canaveral in Florida in 1962. The Cape was the launch site of the Apollo missions. Today, NASA’s facilities at the Cape and elsewhere have expanded greatly.

Apollo

The Moon landing program, using the three-person Apollo spacecraft, was pur­sued with enormous energy at a stagger­ing cost of over $25 billion. Apollo has been compared, in terms of national effort, to digging the Panama Canal or making the first atomic bomb during World War II. In 1967, the Apollo pro­gram survived the tragic setback of a fire inside an Apollo capsule in which three astronauts died. The program triumphed in 1969 with the historic landing of two Apollo 11 astronauts, Neil Armstrong and Buzz Aldrin, on the Moon.

Everything NASA did was very pub­lic. During the Apollo 11 spaceflight and later Apollo Moon landings for example, people all over the world were enthralled by television coverage of the launches and splashdowns, directed from NASA nerve centers that included the Cape Canaveral launch site in Florida and the

Mission Control Center in Houston, Texas. Television audiences were able to see control room staff at work and talk­ing to the astronauts, and they could watch pictures beamed directly from the Moon. NASA space jargon used by the flight controllers, such as “T minus 30 and counting” have since passed into common usage.

Five more lunar landings followed that of Apollo 11. NASA managed to avert disaster when the Apollo 13 mis­sion of April 1970 went seriously wrong. On this mission, the Moon landing had to be canceled after an oxygen tank exploded midway through the outward flight. The three astronauts flew around the Moon and, despite severe power problems, returned safely to Earth. Their safe return was a tribute to NASA’s abil­ity to adapt its technology to cope with the unexpected. In total, twelve astro­nauts walked on the Moon during the

six Apollo lunar landings, which marked the highpoint of NASA’s success.

Many jet planes have very high landing speeds, so tail parachutes are used as extra brakes. Spacecraft returning to Earth have used parachutes to break their fall. For the astronauts of the 1969-1972 Apollo missions, the last stage of their journey was the slowest. They dangled in a capsule beneath bil­lowing landing parachutes that dropped the spacecraft into the ocean, thereby adding the word “splashdown” to the nation’s vocabulary.

The modern wing-parachute or parafoil is highly maneuverable, and parachute jumping has now become an international, competitive sport for indi­vidual jumpers and teams. Freefall sky­diving is a thrilling spectacle at air shows and also has become an enjoyable recreation for many enthusiasts.

SEE ALSO:

• Barnstorming • Ejection Seat

• Skydiving • Takeoff and Landing

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When a propeller spins, its blades cut through the air. The blades work like wings standing on end, whirling around in a circle and producing thrust in a forward direction.

The first airplane propellers were made from a solid block of wood. The angle, or twist, of these early propellers’

To work most effectively, propeller blades (like wings) have to meet the air at the right angle, which is called the angle of attack. The blades follow a complicated path through the air. They are rotating at the same time as the aircraft moves forward, so they follow a spiral path through the air.

In order for the blades to meet the air at the right angle, they have to be twisted.

A propeller’s blades are twisted more near the center than at the tip. Anyone who has ridden a merry-go – round or carousel knows that some­one at the outside edge goes a lot faster than someone near the center.

The reason is that the person on the outside edge has to go a lot farther than someone near the center to make one spin of the merry-go – round. The two journeys take the same time, so the person at the edge travels faster. It is the same for a propeller. The tip of a blade goes faster than the part closer to the center, so the tip does not have to be twisted as much to create the same thrust as the rest of the blade.

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blades could not be changed. The angle of the blades also is called the pitch, so these propellers are called fixed-pitch propellers. They worked most effectively

at one particular speed. They did not work as well when a plane was moving slower or faster than this ideal speed.

Propellers with variable pitch allowed the blades to be twisted a little more or a little less so that the propeller worked better at different speeds. At first, the angle had to be changed by hand, and there were only two or three settings to choose from. Modern variable-pitch propellers auto­matically change the angle of the blades to suit the plane’s speed.

If an aircraft engine breaks down during a flight, air rushing through the propeller blades keeps the propeller spinning. A propeller that spins freely in this way causes drag. Extra drag on one side of a plane acts like a brake and makes the plane turn to that side. Some propellers are designed to prevent this from happening. They have blades with edges that can be turned toward the air to cut their drag. This is called feathering. Some planes can actually reverse their propeller blades so that they blow air forward instead of backward, a process called reverse thrust. It helps cargo planes, such as the military C-130 Hercules, stop a short distance after landing.

The amount of thrust a propeller pro­duces depends on the amount of air it pushes backward and how much it speeds up the air. Making a propeller bigger or spinning it faster produces more thrust. Adding more blades to a
propeller also produces more thrust. The most efficient propellers move a large amount of air and speed it up a little.

Propeller planes are unable to increase their speed indefinitely. When they reach a speed of about 520 miles per hour (840 kilometers per hour), their propellers stop working so well. The problem is that the tips of the blades are moving faster than the speed of sound. The way that air flows around the blades changes at the speed of sound, and so propellers are no longer very good at producing thrust. The fastest that most propeller planes can fly is about 450 miles per hour (720 kilometers per hour).