Category FLIGHT and M ОТІOIM

Fixed-wing airplanes are not the only aircraft that use wings. A helicopter’s rotor blades are actually long, thin wings. High-performance parachutes called parafoils are really inflatable wings. The parachute is made of two layers of fabric with dividers between them, forming a line of pockets, or cells. As the parachute moves along,
air fills the cells and forms a wing shape. The parachutist con­trols and steers the parafoil by pulling control lines that change the wing’s shape.

A flexible fabric hang glider is yet another type of wing. Called a Rogallo wing, this early hang glider was developed in the 1940s by hus­band and wife, Francis and Gertrude Rogallo. When space exploration began, NASA investigated the Rogallo wing as a way of landing the Gemini manned spacecraft. Round parachutes eventually were used instead, but the Rogallo wing was used by other designers, who devel­oped it into the modern hang glider.

Racecars also use wings. However, racecar wings do the opposite job of air­craft wings. They produce a downward force, called downforce, when they cut through air. This pushes the car down harder against the ground, giving its tires better grip, and enabling it to take corners faster without loss of traction.

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SEE ALSO:

• Aerodynamics • Aileron and

Rudder • Bernoulli’s Principle

• Lift and Drag • Stall

Prewar theories that bombing would destroy civilian morale and halt factory production proved inaccurate. The British did not crumble during the Blitz; the Russians moved their factories east out of range of German planes; and German and Japanese workers contin-

WORLD WAR II AVIATION ADVANCES

World War II was a war of air power. During the course of the war, top speeds of fighter aircraft rose from about 350 to 450 miles per hour (563 to 724 kilometers per hour). Bombers flew higher to escape interception: up to 35,000 feet (10,700 meters) by 1945. Naval battles among ships were replaced by long-range air battles between planes flying from aircraft carriers. Factory production methods speeded up manufacture, and technology greatly improved the range, nav­igation, gun power, and bombing accuracy of warplanes. Air transports, such as the C-47 and C-54, carried troops and supplies, and parachutes were used to land them. Radar was the key air invention: It aided ground defenses and also helped pilots locate enemy targets. Air weapons became more destructive as bombs laid waste to cities, and guns and rockets could blow planes apart in midair. For protection, planes had armor plating and self-sealing fuel tanks. By 1944 to 1945, air warfare had been changed forever by new weapons and tech­nology: jet planes, helicopters, the V-1 flying bomb, the V-2 missile, and the atomic bomb.

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SEE ALSO:

After being launched, a spacecraft leav­ing Earth for the Moon or Mars does not need to keep burning fuel. Spacecraft can make use of other methods of propulsion, such as solar sails or ion engines. Once on course and free of Earth’s gravity pull, the engines can be switched off to save fuel as the space­craft coasts through space. This is how the Apollo astronauts traveled to the Moon, a trip that took two-and-a-half days. They fired their engines only to slow down the spacecraft and during their return to Earth.

Although there is no air in space, space is not empty. It contains dust, chunks of minerals, space junk, and streams of radiation flowing out at great speed from the Sun and from other stars.

Stretching into space around Earth is a magnetic field. This magnetism attracts electrically charged particles that form belts, or zones, of radiation. Named the Van Allen radiation belts, these radia­tion zones were unknown until the first U. S. satellite, Explorer 1, encountered them in 1958. The Van Allen belts were the first important scientific discovery made by a spacecraft.

The fastest spacecraft sent from Earth so far have been the solar probes Helios A (1974) and Helios B (1976). Helios B traveled about 150,000 miles per hour (241,350 kilometers per hour) as it orbited the Sun. Although spacecraft are the fastest vehicles ever flown by humans, they are snail-like in space terms, where the distances are unimag­inably immense. The nearest star is 4.2 light years from Earth. So even if a future spacecraft could reach light speed of 186,000 miles per second (299,280 kilometers per second), it would take 4.2 years to get there.

To fly astronauts to Mars and back using existing spacecraft would take eighteen months. Keeping astronauts alive, healthy, and able to work during such a long mission poses great chal­lenges to space science. Humans are not designed for an airless, weightless environment. A manned spacecraft must provide everything needed for human life support-air, water, food, fuel, energy, waste disposal, and exercise. Long periods of spaceflight weaken the body’s muscles. So great are the chal­lenges that some scientists believe that

he Space Shuttle was the world’s first reusable spacecraft and the first spacecraft with wings. The Space Shuttle can carry seven astronauts into space, stay in orbit for about two weeks, and then fly back to Earth to land on an airstrip.

The Shuttle Concept

Until the first Space Shuttle flew in 1981, all spacecraft (manned craft, satel­lites, and space probes) were launched by multistage rockets. Such rockets and the spacecraft they carried could be used just once. Only the spacecraft itself reached space; the discarded rocket stages fell into the sea or burned up in the atmosphere. The Space Shuttle was planned as a more economical vehicle
that could make regular trips into space. It has no rival. The Soviet Buran shuttle spacecraft, similar in appearance, made only one flight, without a crew, in 1988; it was thereafter canceled.

In 1969, a Space Task Group set up by President Richard Nixon’s adminis­tration suggested several new space projects. One was a reusable spacecraft, capable of flying one hundred or more missions. The result was the Space Shuttle, known to NASA as the Space Transportation System (STS). The main contractor was North American Aviation (later part of Rockwell International, now part of Boeing). Other contractors responsible for supplying the engines

О A view inside the Space Shuttle shows the giant engines, the cargo bay, and the flight deck and mid-deck where the astronauts live.

Air

control

thrusters

Electrical system fuel cells

and fuel tanks, were Morton Thiokol, Martin Marietta, and Rocketdyne.

The first Shuttle to fly was Enterprise, which was used for prelimi­nary flight and landing tests from 1977. These tests included flights on top of a modified Boeing 747 airplane. Enterprise never actually went into space. Five Space Shuttles have flown in orbit. The first operational Space Shuttle, delivered to NASA in March 1979, was Columbia, which made its first space flight on April 12, 1981, and remained in service until it was destroyed in a tragic accident in 2003. Challenger, which arrived at Kennedy Space Center in July 1982, was the first Space Shuttle to be lost in an accident, in January 1986. The three Space Shuttles currently operational are Discovery, delivered in November 1983; Atlantis, delivered in April 1985; and Endeavour, which was built to replace Challenger and arrived at Kennedy Space Center in May 1991.

The wings, fin, and stabilizers keep an airplane flying straight and level. A pilot, however, needs the ability to make an airplane turn, climb, dive, and roll. Parts of the aircraft’s wings, fins, and stabilizers are hinged so that they can swivel. These moving parts are called control surfaces. The control surfaces are

the ailerons in the wings, the elevators in the horizontal stabilizers, and the rudder in the vertical fin. When the pilot moves the flight controls in the cockpit, the control surfaces move and change the aircraft’s balance. The aircraft responds by turning, pitching its nose up or down, or rolling.

An aircraft’s ability to produce the amounts of pitch, roll, and yaw the pilot wants is called the aircraft’s response. Different types of aircraft often need a different response. For example, a fast response is crucial for fighter planes in combat. Modern fighters are deliberately designed to be unstable. Flight comput­ers keep a fighter plane under control until the pilot needs to make a fast maneuver, when the plane’s lack of sta­bility enables it to respond instantly to
the controls. Airliners do not need the rapid response of fighters. An airliner is more stable and responds more slowly to its controls.

n aircraft’s tail helps to keep it stable in the air. The tail’s con­trol surfaces make the aircraft climb, dive, and turn to the left or right.

An airplane’s tail acts like an arrow’s feathers or a firework rocket’s long stick. The tail keeps the plane pointing in the right direction, nose first. Without a tail in place, most airplanes would crash to the ground. The Northrop B-2 Spirit stealth bomber, for example, has no tail and is therefore a very unstable aircraft. It only can be flown with the help of a powerful flight computer.

Stabilizers

A typical airplane tail has a vertical sta­bilizer, or fin, that stands up on top of the fuselage, and a horizontal stabilizer, or tailplane, which sticks out from either side of the tail fin. The fin has a moving part at the back called the rudder. When the rudder is turned to the left, the air
flowing around it pushes the plane’s tail to the right, and the aircraft’s nose turns to the left. When the rudder turns to the right, the aircraft’s nose turns to the right.

The tailplane has moving parts at the back called elevators. The elevators con­trol the aircraft’s pitch. When the eleva­tors tilt up, air flowing around them pushes the aircraft’s tail down and brings the nose up. When the elevators tilt down, the aircraft’s nose tips down as well.

Another method for achieving vertical flight uses separate engines for lift and for forward flight. The lift engines are used to get airborne, and then separate forward thrust engines propel the plane normally. Once the plane is flying forward and the wings are generating lift, the lift engines are shut down. The disadvantage of this design is that the aircraft has to carry the dead weight of the lift engines, which reduces its performance.

One example of this type of aircraft is the Russian Yakovlev Yak-38 Forger. It has three jet engines. Two lift engines behind the pilot blow air straight down. The main engine provides thrust from two nozzles behind the wing. These nozzles can rotate to direct the jet exhaust downward to provide extra lift. The Yak-38 serves on Russia’s Kiev class aircraft carriers.

orld War I began in Europe in 1914, and the United States entered the war in 1917. Remembered for the terrible slaughter of trench warfare on the Western Front, the “Great War,” as World War I became known, was the first war in which air­planes played an important part.

LEARN-EARN

О A World War I poster encourages volunteers to enlist in the Air Service, part of the U. S. Army. At the time, there was no separate U. S. Air Force. The poster reflects the aircraft of the period, including airships.

The Role of Aircraft

Until 1914, military strategists regarded command of the sea as the key factor in international warfare. Britain, Germany, and the United States had the biggest navies. When World War I began, air­planes were still a novelty. The fastest airplane had a top speed of only 100 miles per hour (160 kilometers per hour) and a range of about 100 miles (160 kilometers) before needing to refuel.

In the nineteenth century, balloons and airships had been used in wars, mostly for observation and for evacua­tion of civilians. The military had yet to find uses for the airplane. In 1912, Britain had set up a Royal Flying Corps, but it had very few aircraft. Germany had the largest air force, with more than 200 airplanes plus Zeppelin airships. The U. S. Army had purchased its first air­planes in 1913. No nation had assembled a large air force.

In the four years of World War I (1914-1918), the airplane became a much more formidable weapon. Fighter planes battled in aerial combats called dogfights. For the first time, cities were bombed from the air by airships and air­planes. The warring nations formed air forces or aviation divisions within their armies and navies. War would never be the same again.

Dates of birth: Wilbur: April 16, 1867; Orville: August 19, 1871.

Places of birth: Wilbur: Millville, Indiana; Orville: Dayton, Ohio.

Died: Wilbur: May 30, 1912; Orville: January 30, 1948.

Major contribution: Achieved the first sustained, powered, controlled airplane flight; built the first practical powered airplane; built the first practical passenger-carrying airplane.

Awards: Orville: Collier Trophy.

n December 17, 1903, Wilbur and Orville Wright flew the first sus­tained, powered, controlled air­plane flight at Kitty Hawk, North Carolina. The Wrights continued experi­menting with airplane designs and made several important advances. They helped promote aviation across the United States and in Europe.

Early Life

The Wright brothers were the sons of Milton and Susan Wright. Their father was a church minister. Years after their success, the Wrights said they first became interested in flying in 1878 when their father brought home a toy helicopter powered by a rubber band. Intrigued when the toy flew, the boys played often with it and experimented by making their own versions of it. Their mother, who often made toys and

household appliances herself, encour­aged the brothers’ interest in flight.

Wilbur graduated from high school, but before starting college he suffered a serious injury while playing hockey. He remained at home, helping his father with church business and caring for his sick mother until her death in 1889. During this time, Wilbur read constantly.

By the time their mother died, Wilbur’s younger brother Orville had persuaded Wilbur to join him in opening a print shop in their hometown of Dayton, Ohio. The brothers began pub­lishing a small newspaper, but they failed to make money with the paper and eventually closed the business. In 1892, the brothers opened a successful bicycle shop where they built, sold, and repaired bikes.

Spaceflight began in the mid­dle of the twentieth century, but scientists and writers had imagined the possibility long before. In the seventeenth cen­tury, physicist Sir Isaac Newton set out laws of motion that determine the way in which objects move through space. Fantasies about space travel came from science-fiction writ­ers such as Jules Verne. In his 1865 book From the Earth to the Moon, Verne wrote of people flying to the Moon in a capsule fired from a huge cannon. In 1898, H. G. Wells imagined Martian spacecraft invading Earth in The War of the Worlds. At this time, people could only study the Moon and Mars by peering through optical telescopes, and there were many fanciful notions about alien life-forms on distant worlds.

Russian teacher Konstantin Tsiolkovsky (1857-1935) fig­ured out the mathematical principles of spaceflight by rockets. In 1923, Hermann Oberth (1894-1989) wrote The Rocket into Planetary Space, a book that predicted spaceflight.

Johannes Winkler Oberth (1897-1947), along with other German enthusiasts, formed the Society for Space Travel. One of its members was Wernher von Braun (1912-1977), who helped design the V-2 rocket of World War II and later worked on the U. S. space program. In 1926, American Robert H. Goddard (1882-1945) launched the world’s first liquid-fuel rocket.

The American Interplanetary Society was founded in 1930 by G. Edward Pendray, David Lasser, Laurence Manning, and others. In 1934, it became known as the American Rocket Society.

In 1963, it became part of the American Institute of Aeronautics and Astronautics. The American Rocket Society and the British Interplanetary Society both helped stimulate public interest in space­flight and encouraged test flights of rockets at a time when governments had little interest in spaceflight.