Category FLIGHT and M ОТІOIM

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.

The Space Shuttle design has three main elements: the spacecraft itself, called the orbiter; an external propellant tank; and two solid-fuel rocket boosters. The orbiter looks like a stubby airplane with small, swept-back wings. The external tank holds fuel for the spacecraft’s main engines. The boosters provide most of the lift during the first 2 minutes of flight. All elements of the Space Shuttle are reused except for the external pro­pellant tank. The Space Shuttle’s two

TECHibTALK

THE SPACE SHUTTLE

Length: 122 feet (37 meters). Wingspan: 78 feet (24 meters).

Length with fuel tank and boosters: 184 feet (56 meters).

Cargo bay: 60 feet by 15 feet (18 meters by 4.5 meters).

Maximum payload: 50,000 pounds (22,700 kilograms).

Orbit altitude: about 185-250 miles (300-400 kilometers).

Orbit speed: 17,321 miles per hour (27,870 kilometers per hour).

Landing speed: about 215 miles per hour (345 kilometers per hour).

_____________________________________________ J

solid-fuel boosters burn out 2 minutes after liftoff, at a height of about 28 miles (45 kilometers). They are landed by parachutes and used again. The external tank holds more than 1.57 million pounds (713,000 kilograms) of liquid hydrogen and liquid oxygen. When this fuel is used up, after 8 minutes, the empty tank is jettisoned over the ocean just before the Space Shuttle enters orbit. The tank then burns up in Earth’s atmosphere.

Once in orbit, a Space Shuttle pilot can fire small thruster motors to maneu­ver the craft. The thrusters may be used to change direction and to slow down, for example when docking with the International Space Station.

If an aircraft is to be stable and easily controlled, it must be well balanced. An aircraft balances around a point called its center of gravity, or center of mass. When fuel, passengers, cargo, or any other weight is added to an aircraft, it must be spread evenly throughout the aircraft. Too much weight at the front moves the center of gravity forward and makes the aircraft nose-heavy. Too much weight at the back makes it tail – heavy. More weight on one side than the other side makes it roll. An aircraft’s center of gravity must not be allowed to move too far in front of, or behind, its ideal position. If this happens, the air­craft can become difficult to fly or even dangerously unstable.

Military transport aircraft have a crew member called the loadmaster. Part of the loadmaster’s job is to place the cargo and passengers on board so that the plane’s center of gravity stays within its allowed limits. The center of gravity moves as an aircraft burns off fuel during a flight, so the loadmaster must take this into account.

An airliner’s weight and the position of its center of gravity are calculated before every flight. The amount of fuel it has to carry depends on its weight. A heavier aircraft needs more fuel. To cal­culate the weight and the position of the center of gravity, the crew needs to know approximately how much the fuel, passengers, and baggage weigh.

Most of the weight carried by an air­liner is fuel, and so the amount of fuel pumped into the aircraft’s tanks is meas­ured. The weight of each gallon, or liter, is known, so the weight of the fuel can be calculated. Most of the fuel is stored in the wings on each side of the aircraft.

The baggage is weighed too, but what about the passengers? Passengers are not weighed individually. Instead, air­lines use standard passenger weights, based on an average and multiplied by the number of passengers, to arrive at the total weight of all the passengers.

N

J

HEAVY PASSENGERS

People are getting heavier. The weight of the average person has been increasing since the standard weights used by air­lines were set in the 1990s. Passengers also are bringing more carry-on baggage onto airplanes, and airlines have had to take this extra weight into account. Since the 1990s, the average passenger weight, including carry-on baggage, has increased from 170 pounds (77 kilo­grams) to 190 pounds (86 kilograms).

In winter, passengers wear more clothes, so the average passenger weight in winter increases further to 195 pounds (88 kilograms).

In 2005, because of these changed statistics, the U. S. Federal Aviation Administration (FAA) issued new figures for standard passenger weights. The average weight of an adult man with carry-on baggage was increased from 185 pounds (84 kilograms) to 200 pounds (91 kilograms) in summer and 205 pounds (93 kilograms) in winter. The weight for an average woman with carry-ons was increased from 145 pounds (66 kilograms) to 179 pounds (81 kilograms) in summer and 184 pounds (83 kilograms) in winter. The weight for children age two to twelve years old was increased from 80 pounds (36 kilograms) to 82 pounds (37 kilo­grams) in the summer and 87 pounds (39 kilograms) in winter.

J

The tailplane is usually at the bottom of the fin, but some aircraft have theirs fitted halfway up the fin. This type of tail is called a cruciform tail. The word “cruciform” means cross-shaped, and a cruciform tail forms a cross shape when viewed from the front or back.

The tailplane also can be at the top of the fin. This type of tail is called a T-tail because the tail fin and tailplane form a T shape. Cruciform tails and T-tails are common in business jets, which often have their engines mounted on each side of the tail. Mounting the tailplane higher up the tail fin places it out of the way of the engines.

A few aircraft have been built with a V-tail. This has two fins at an angle, forming a V shape. Each fin has a moving part at the back, which is called a ruddervator because it works as both a rudder and an elevator. The F-117 Nighthawk attack plane has a V-tail. The V-tail causes less drag than other designs because it has fewer surfaces, but the aircraft’s tail has to be made stronger, and its control system is more complicated.