Category FLIGHT and M ОТІOIM

ollution is the process of making the environment dirty, dangerous, or in other ways unpleasant or unhealthy for people, animals, and plants. Flying contributes to pollution through the emissions from airplane engines and through noise and environ­mental damage around airports.

Transportation is a major source of air pollution in the United States and other industrial nations. Jet engines, like automobile engines, burn carbon-based fuel. During the burning process or com­bustion, airplane engines give off car­bon monoxide, carbon dioxide, hydro­
carbons (compounds of carbon and hydrogen), and nitrogen oxides (com­pounds of nitrogen and oxygen). These substances are all pollutants, and too many of them in the atmosphere can have damaging effects on people, on animals, on plants, and even on build­ings. Polluted air is unhealthy to breathe. Heavy concentration of pollu­tants around cities can form smog, reducing visibility and air quality and endangering the health of people.

Scientists believe that carbon-based pollutants are causing damage to Earth’s atmosphere. A buildup of carbon diox­ide gas in the atmosphere from burning fossil fuels-such as gasoline and avia­tion fuel-is thought by many experts to contribute to the greenhouse effect. The gases trap heat from sunlight, therefore contributing to global warming and climate change.

High-flying jet aircraft emit those gases close to Earth’s surface and at higher altitudes. The primary gas in jet engine emissions is carbon dioxide, which can linger in the atmosphere for up to a hundred years. Aviation emis­sions account for up to 4 percent of all global carbon dioxide emissions from the burning of fossil fuels. Carbon diox­ide combined with other airplane exhaust gases could be having a much greater impact on the air than carbon dioxide alone.

Most legislation passed in recent decades to cut air pollution has been directed at industry and automobiles. With aviation growth at around 5 per­cent a year, however, the development of cleaner aircraft engines is vital.

Airports also are a source of pollu – tion-not simply because of the number of airplanes using them, but because a busy airport draws in thousands of cars and trucks every day. Airport buildings and handling facilities consume a lot of energy and produce a lot of waste. Even the chemicals used to de-ice airplanes in winter pose a pollution risk to the soil and the water cycle.

NOISE POLLUTION

As air traffic increases, there are concerns about noise pollution. Anyone who has stood on a runway close to a jet plane taking off knows that it is very noisy. The loudness is measured in decibels. A jet plane taking off can reach 130 decibels. Supersonic planes also make a sonic boom. Protests about the boom ended airline plans to fly the Concorde on transcontinental super­sonic flights in the 1970s. Modern turbofan engines are more efficient and less noisy than the engines of fifty years ago, but many airports suspend flights at night so that local residents can sleep undisturbed.

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Some campaigners argue for cuts in flights or at least increased airport and airline taxes-and thus higher fares – to reflect the true environmental cost of flying. Aircraft manufacturers respond that new airplane engines are becoming increasingly efficient and clean. They also say the introduction of larger air­planes means fewer flights, less fuel burned, and therefore less pollution.

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SEE ALSO:

• Aircraft Design • Airport • Engine

• Fuel • Future of Aviation

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Solid-fuel rockets are the simplest and oldest type of rockets. Aircraft have been armed with solid-fuel rockets since World War I, when they were used to attack airships and observation bal­loons. Rockets fired from one aircraft at another aircraft are called air-to-air rockets. The airships and balloons were filled with hydrogen, which burned if a flaming rocket flew into it. The problem was that the planes of the day also were made of flammable materials, so firing rockets from them was dangerous. The rockets also were inaccurate and rarely hit their targets.

Small air-to-air rockets were used again in World War II. They enabled fighters to attack bombers without com­ing within range of the bombers’ guns. These small rockets were unguided-they were aimed simply by pointing the

О The Space Shuttle has two solid rocket boost­ers (SRB) that are strapped to its external fuel tank. The SRB are discarded about 2 minutes after liftoff, and they fall back to Earth to be retrieved and reused.

Robert Hutchings Goddard was an American scientist and inventor who developed the modern liquid-fuel rocket. He received patents for a liquid-fuel rocket and a two – stage rocket in 1914. In 1919, Goddard wrote a paper called "A Method of Reaching Extreme Altitudes," in which he talked about sending a rocket to the Moon. He was ridiculed at the time for even suggesting such a crazy idea. In 1926, Goddard suc­ceeded in building and launching the first liquid-fuel rocket. Powered by gasoline and liquid oxygen, the small rocket rose to a height of 41 feet (12 meters). Goddard went on to build bigger and more powerful rockets. Some of them climbed higher than

9,0 feet (2,740 meters) and went faster than the speed of sound. Goddard was the first person to steer a rocket by using vanes in the rocket exhaust, and he designed the first gyroscopic systems for guiding rock­ets. NASA’s Goddard Space Flight Center is named in his honor.

C Robert Goddard displays his liquid oxygen-gasoline rocket before its successful launch in 1926.

whole plane. In the 1950s, air-to-air rockets were replaced by guided missiles.

Solid-fuel rockets are used to help launch spacecraft. Space launch rockets are liquid-fuel rockets, but they can be made more powerful by strapping solid- fuel rockets around them. The solid rock­ets provide extra power for liftoff. Extra rockets used like this are called boosters. The Space Shuttle is launched with the
help of two solid rocket boosters (SRB). They burn powdered aluminum fuel with ammonium perchlorate oxidizer. The propellants are mixed as liquids and then set hard in a mold. A hole runs through the center of the rocket. When the propellants are ignited, they burn from the inside out. Once solid-fuel rockets have been lit, they cannot be turned off.

In the spring of 1909, Sikorsky built his first real helicopter. However, the machine would not fly. Another version failed to fly the following year, and Sikorsky decided to abandon the effort. As he later explained, “I had learned enough to recognize that with the exist­ing state of the art, engines, materials, and—most of all—the shortage of money and lack of experience. . . I would not be able to produce a successful helicop­ter at that time.”

Sikorsky turned his attention to designing airplanes, producing several models and flying them himself. In 1911, he earned an international pilot’s license, becoming just the sixty-fourth person in the world to have one. That year, Sikorsky’s S-5 plane set records by carrying three people more than 30 miles (48 kilometers) at 70 miles per hour (about 113 kilometers per hour). Another of his planes won an award at an air show the next year and took first prize in a competition held by the Russian armed forces. This success earned Sikorsky a job with a Russian company, where he worked on manufac­turing airplanes.

In 1913, Sikorsky produced a new design he called the Grand. This large airplane was powered by four engines – the first flying machine to have more than one. It also was the first to have the pilot and passenger areas fully enclosed. The Russian army used several dozen aircraft of this design as bombers during World War I (1914-1918).

Russian participation in the war ended when communists took control of the nation’s government and pulled the country’s troops out of the conflict. Sikorsky left his homeland in 1919 and eventually reached the United States.