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The knowledge that steam could produce energy is about 2000 years old. An Egyptian engineer called Hero made a machine called „aeolipile“ in which steam drove round a metal sphere. The aeoliopile was a toy with no practical use, but it showed that steam could be a source of energy.

The modern history of steam power began with a French scientist, Denis Papin (1647-1712). He invented the pressure cooker and a simple steam pump to provide the power of fountains. In 1690 Papin had the idea of building an engine in which steam would raise a piston inside a cylinder, creating a vacuum as it rose. This was the principle of later steam engines, but Papin never managed to make an engine that worked.

The first successful steam engine arose out of the urgent need to pump water out of flooded mine shafts. In 1698, an English engineer, Thomas Savery (c.1650-1715), invented a steam pump. He called it the `Miner`s Friend`. It had a cylinder which was filled with steam from a boiler. When the cylinder was cooled by pouring cold water on the outside, a partial vacuum was created. The vacuum drew water into the cylinder from the mine shaft. The Miner`s Friend would pump water up only about six metres. If the water was any deeper, the engine became unsafe and sometimes even blew up. This engine used a huge amount of coal to raise steam.

To people who had been used to the quiet and leisurely pace of horse-drawn transport, the speed, power and noise of steam locomotives was terrifying.

The first victim of a railway accident was a British cabinet minister, Sir William Huskisson (1770-1830). At the opening of the Liverpool and Manchester Railway in 1830, he stepped into the path of the oncoming train and was killed.

Some even believed that rail travel could be dangerous. ln the 1830s, an eminent Irish scientist, Dr Dionysius Lardner (1793-1859), warned that travelling at a speed of forty-eight kilometres per hour could make the brain fall apart. In Britain, Queen Victoria was persuaded to make a train journey from Windsor to London in 1842 to show that rail travel was safe.

Country people in particular were opposed to railways. They had good reason, because the noise and smoke of trains ohen frightened livestock grazing by the line and made horses throw their riders. Another problem was that sparks from locomotive chimneys came down in line-side fields and set fire to growing crops. But farmers later found that they benefited from railways, because trains could get their goods to market more quickly than before.

At this point, the best-known name in the history of steam comes into the story. James Watt (1736-1819) was a Scottish instrument maker and repairer working at the University of Glasgow. In 1763, he saw a Newcomen engine for the first time when the university sent a model in for repair. Watt was a true scientist, always questioning and experimenting. Soon he was working on ways to improve the efficiency and cut the fuel consumption of the Newcomen engine.

Watt`s first improvement was to separate the heating and cooling stages of the engine`s operation. Having to heat the water and then cool it in the same cylinder made the Newcomen engine slow and was also the main cause of its heavy use of fuel. Watt designed an engine with a separate condenser where the cooling process could take place. Meanwhile, the cylinder stayed hot all the time. This meant that there was no pause while the cylinder reheated.

The addition of a condenser was only one of the improvements made by James Watt. Of the others, the most important for the future of transport was his introduction of a set of gears which he called `sun and planet`. Until then, steam engines could produce only an up-and-down movement. The piston made to rise and fall by steam in the cylinder was attached to a beam which also rose and fell. Watt`s sun and planet gear enabled the piston to turn a gear wheel, the `planet`, which meshed with a second gear, the `sun`. The `sun` was connected to a wheel shaft and made it turn.

Watt had found the way to change the up-and-down movement of the piston into a rotary movement. In other words, Watt`s sun and planet gears could make steam engines turn wheels. The possibility of steam-powered transport had at last become a reality.

This was the first time that a steam train had travelled on rails, but the idea of using rails to provide a more even surface than the bumpy, rutted roads of those days was not new. Wooden tramways had been used for horse-drawn transport in coal mines for at least 200 years. About 1800, some of these wooden tracks began to be replaced by longer-lasting cast iron rails. It was Trevithick`s idea of bringing together the iron tramway and the steam locomotive that marked the launch of the railway age.

At first, progress was slow. In 1808, Trevithick built a small circular railway track in London to demonstrate his new locomotive, Catch-Me-Who-Can. Plenty of people came to see it, but the railway was still seen as a toy, not as a serious means of transport. Trevithick lost heart and turned to other interests.

Meanwhile, steam locomotives had caught the attention of another Englishman, George Stephenson (1781-1848). In 1814, he built his first locomotive for the colliery where he was the engineer. Eleven years later, his engine Locomotion hauled the first railway train on the newly-built line, forty-two kilometres long, between Stockton and Darlington in northern England. This was the first railway in the world open to the public, with regular services in each direction. But people were still unsure about the safety of steam travel. Locomotives were used to haul coal trains on the Stockton to Darlington line, but passenger services were horse-drawn.

Railways made a vast difference to the lives of ordinary people. Travel was faster and easier than it had ever been. Soon, people were living at a distance from their work and commuting each day by train. The railways made travelling for holidays possible. They also made the transport of goods from place to place easier and cheaper. Fresh meat and vegetables, milk and other dairy products became easier to buy. New towns grew up close to the railway lines. Builders no longer had to depend on local materials, and farmers could transport their cattle to market by train instead of driving them slowly along the roads.

Army generals, too, were quick to realize that railways were an efficient method of transporting troops. The first use of railways in war was in the Crimean War of 1853 to 1856 when Britain and France fought Russia. A temporary railway was built to carry British troops into battle and to evacuate the wounded.

Within fifty years of the opening of the first steampowered railway, the steam locomotive had conquered almost the whole world. By 1869, it was possible to cross the United States from the Atlantic to the Pacific by rail. The east-west link across Canada was opened in 1887. India`s and Australia`s first railways opened in 1854, and Africa`s in 1870. Some of these lines gave links with the outside world to places that had been almost completely cut off before.

Most of the world`s railways now operate with diesel or electric locomotives, but if it had not been for the pioneers of steam many would not have been built at all.

Soon after the invention of the steam engine, inventors began to wonder if steam could free sailors from the uncertainties of relying on the wind for power. American engineers led the way in the development of steam for shipping. So it came that the first steamships were built about 1750.

Just as railways opened the way to the interiors of the continents, so steamships brought the continents closer together. Farmers and manufacturers found new markets for their products overseas, carried quickly and reliably by steamer. The steamship was also responsible for large movements of populations, as millions of people from Europe crossed the oceans to begin new lives in North America, Australia and New Zealand.

Within less than a hundred years, steam had changed the world. In 1800, the fastest means of transport on land had been on horseback. At sea, travellers had depended on the way the wind blew. By 1900, there were few large towns or cities in the world without a railway station, and travel by rail had become fast and cheap. At sea, a network of regular steamship services carried passengers and cargoes across the world.

There is an important difference between a steam engine and an internal combustion engine of the kind used in cars and trucks. In a steam engine, the fuel is burned in a separate boiler to make steam, which in turn provides the force to make the engine work. In an internal combustion engine, the fuel is burned inside the engine itself. This makes the internal combustion engine a lighter, more compact and more easily controllable machine than the steam engine.

The story of the internal combustion engine begins over 300 years ago with a Dutch scientist called Christiaan Huygens (1629-95). About 1680, he built an engine which used gunpowder as fuel.

The explosion of the gunpowder raised a piston inside a cylinder, which fell again as the hot gases from the explosion cooled. Today, it sounds rather strange and highly dangerous to run an engine on gunpowder, but Huygens had the right idea. All internal combustion engines are driven by explosions. A modern car engine works because of the explosions of a mixture of fuel and air which take place all the time the engine is running.

The idea of internal combustion was forgotten in the excitement over steam, and it was not until the 1840s that a French inventor, Etienne Lenoir (1822-1900), returned to it. His engine ran on coal gas. It worked well, but it used so much gas that it was not a serious rival to the steam engine.

As with many important inventions, no one person can be described as the inventor of the modern internal combustion engine. Many scientists and inventors tried out different ideas in the middle of the nineteenth century. But in 1876, a German engineer, Nikolaus Otto (1832-91), built the first successful internal combustion engine. His engine was fuelled by coal gas, but was not intended for transport. The aim was to find something more compact and convenient than the steam engine to power pumps and factory machines.

The oil industry in those days was very small. Oil was used only for lighting and cooking, and as a lubricant. Some engineers began to experiment with oil as a fuel for engines. Their work developed along two distinct lines, and led to the two main types of internal combustion engines that we have today: the diesel engine and the petrol engine. The petrol engine was the first to be fitted to a car.

One of Otto`s assistants was Gottlieb Daimler (1834-1900). Daimler left to set up his own business, and, in the mid-1880s, he began to experiment with petrol as a fuel. This was mixed with air and drawn into the engine at exactly the right moment when it would explode and drive the piston.

On his third attempt to build his engine, Daimler was satisfied with its performance and fitted it to a bicycle. In 1886, he tried this out on the roads. The next year, he took a four-wheeled carriage, removed the shafts used to attach a horse to it and fitted his engine. This was the first `horseless carriage`.

In the same year, another German engineer, Karl Benz (1844-1929), fitted a similar engine to a tricycle. He went on to build four-wheeled vehicles.

Daimler`s and Benz`s cars were the first to go into production for sale to other people. Benz built his own cars, but Daimler sold his engines to a French company, Panhard and Levassor, which built bodies for them. These were the first car bodies that did not copy the design of horse-drawn carriages. The 1894 model had many modern features such as a metal chassis, a bonnet over the engine, and clutch, brake and accelerator pedals.

The first cars were expensive, and were regarded more as toys for rich people than as a serious means of transport. Owners also had to be prepared to have a sense of adventure and an understanding of engines, because breakdowns happened frequently.

As engines became more reliable, more people wanted cars, and as more cars were made, the price of them went down. By the 1920s, motoring was beginning to become an everyday experience for millions of people.

While Daimler and Benz were experimenting with petrol engines, another German engineer had been working on an internal combustion engine which worked in an entirely different way. Rudolf Diesel (1858-1913) gave his name to the kind of engine fitted to trucks, buses and some cars.

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Diesel`s engine used an oil similar to paraffin instead of petrol. It drew air into the cylinder, where it was compressed by the piston. When this compressed air met the fuel which had been forced into the cylinder, the mixture ignited and there was an explosion, forcing the piston upwards.

Diesel patented his engine in 1892, but it was not until 1898 that he demonstrated it at an exhibition in Munich. It was an immediate success despite its size and weight, and was quickly adopted for use in factories. Later, lighter and more compact versions were developed for heavy road vehicles, tractors and eventually for cars.

The internal combustion engine changed the lives of everyone in the twentieth century. We rely on it for personal transport, for deliveries, for emergency services such as fire-fighting and in countless other ways. But it has also brought problems. The most serious of these is air pollution from vehicle exhausts, which has ruined the quality of the air in many cities. The challenge is to develop a means of personal transport which does not demage our health.

Although jet aircraft were not flown regulary until the 1940s, the idea of an engine producing power by shooting out a stream of gases and compressed air behind it goes back a long way. It is said that the British scientisr Sir Isaac Newton (1642-1727) thought of using the idea in a stream carriage as long ago 1687. Two hundred years later an aeroplane drives by steam jets was designed, although it was never built. Then, at the beginning of the twentieth century, the gas turbine was invented. This works by using hot exhaust gases to drive a turbine, in a similar way to a jet engine. Gas turbines were used in industry, and some people began to wonder if the could be adapted to power aircraft.

One such person was a British Royal Air Force officer, Frank Whittle (1907- ). Whittle began researching the idea of a gas turbine aircraft engine while he was still a student. By the time he was twenty-three, he had designed a jet engine for use in aircraft, although he lacked the money to build one himself. His RAF employers allowed him time off to work on the project, but showed little interest in the results.

Finally, in 1937, Whittle found some backers to finance the building of his jet engine. This was given its first test runs in the same year. There were teething troubles, but Whittle and his team carried on. Then, in 1938, with war looming, the RAF began to take an interest in Whittle`s work and gave him the support he needed to speed it up. Two years later, the engine was ready to go into production, and Britain`s top engineering firm, Rolls-Royce, was chosen to make it.

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When peace came in 1945, the jet technology that had been developed for use in warplanes could be applied to civilian aircraft. One of the problems for airlines before the war had been the inefficiency of piston engines. This meant that they had to carry huge amounts of fuel, and even then had to make frequent stops to take on more. The greater efficiency of jets made the development of jet airliners attractive, especially for intercontinental flights. Not only could jets fly faster, they could also fly higher. This improved their efficiency even more, and also gave a smoother and more comfortable flight for passengers as jets could fly above the clouds, so avoiding any bad weather.

As the new jet airliners carrying larger numbers of passengers came into service, the cost of air travel fell. In the USA, even in the 1930s, it had become commonplace to make long journeys between the major cities by air. Now, all over the world, flying lost its pre-war luxury image and became the normal means of travel for people going abroad on holiday or business trips. A new generation of airliners, the huge jumbo jets, was built to cope with the vast numbers of

people who now wanted to travel by air.

A whole family of jet engines had been developed from the simple original design. One of these was the turbofan. The front cover of the engine conceals a fan which sucks air in and passes it to a compressor before the air and fuel mixture is ignited. The turbofan operates more quietly and uses less fuel than other types of jet engine. Turbofans were used to power the new wide-bodied jumbos.

Once the jet engine had been developed,. the race was on to build engines that would drive aircraft at ever greater speeds. The lead was taken by the world`s major air forces. They wanted jet fighters that could fly faster than the enemy`s, and jet bombers that could fly high and fast, out of reach of enemy defences.

`Breaking the sound barrier` became an important target. Sound travels in air at about,1,160 kilometres per hour. At one time, it was thought that at speeds like this the pressure on aircraft frames, and on the bodies of their pilots, would be too much. This was disproved in 1947 when an American Bell X-1 aircraft, powered by a rocket engine, broke the sound barrier without mishap. There was no reason why suitably designed aircraft should not fly at supersonic speeds.

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