My Science School

MODERN CARS

All modern cars, from the smallest urban car to the fastest racing cars, have similar basic features. Wheels and suspension allow the car to roll smoothly along the road. Tyres on the wheels grip the road surface, allowing the car to accelerate, brake and corner without sliding.

Power from the engine is transferred to the wheels by the transmission, including the gears. The fuel and exhaust systems supply fuel to the engine and carry away waste gases. The electrical system supplies electricity to the engine’s spark plugs, the car’s lights and other electrical gadgets.

A stretch limousine is a chauffeur-driven luxury car used for special occasions such as weddings. Inside are large, comfortable seats, where passengers can enjoy drinks from a bar and even watch television.

All the car’s parts are supported by a rigid body shell, which also protects the driver and passengers. Modern cars have many advanced features which make them more efficient, and easier and safer to drive. These include computerized engine-management systems which control the flow of fuel to the engine, navigation computers which give the driver directions, anti-lock brakes which prevent skidding, and air bags which protect the driver in an accident. Many of these features were originally developed to improve the performance of racing cars, but have become standard on road cars.

AERODYNAMICS

The way air flows around a moving body is called aerodynamics. As cars move along, the air flowing around them tries to slow them down. The effect is called drag, and it prevents cars from continuing to speed up. The more streamlined the shape of a car, the lower the drag on it, and so the faster its top speed. Racing cars have special aerodynamic features, such as wings that create down-force. These force a car’s tyres on to the road, increasing grip and allowing the car to corner more quickly without skidding sideways.

Aerodynamics are especially important in very high-speed cars, such as Thrust SSC, which holds the land-speed record of 1227.723 km/h. It is the only car to have gone faster than sound.

All road vehicles have similar features to cars, but the features are often specialized. For example, large haulage trucks have many wheels to spread their heavy load. Off-road vehicles, such as dumper trucks, have large wheels with chunky tyres for good grip in the mud. Road-rollers have solid steel wheels.

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SUBMARINES

A submarine is a vessel that can travel submerged under the water as well as on the surface. A submarine needs an extremely strong hull to resist the pressure deep under water. Ballast tanks in the hull are filled with water to make the submarine heavier so that it dives. The tanks are “blown” with air to empty them and make the submarine surface again.

While submerged, submarines are propelled by battery-powered electric motors that do not produce dangerous exhaust fumes. On the surface, diesel engines take over. They recharge the batteries at the same time.

Huge military submarines such as USS George Washington lurk under the water and attack enemy ships with torpedoes. Nuclear-powered submarines can stay submerged for months.

A submersible such as Alvin is a miniature submarine. Submersibles are mostly used for research in the ocean depths. Robot submersibles also carry out underwater repairs on oil rigs.

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MODERN SHIPS

Modern ships and boats can be categorized by the jobs they do. Merchant ships include cruise liners, ferries, cargo ships, and utility ships, such as dredgers and tugs. Military ships include warships and support ships, called auxiliaries. There are also numerous different types of fishing boat and leisure craft, from luxury yachts to sailing dinghies.

Small cargoes are carried in standard-sized metal boxes called containers on container ships, which are loaded and unloaded at dedicated container terminals. Cargoes such as ores, coal and grain are carried by bulk carriers. Oil and other liquids are carried by tankers.

The main part of a ship is its hull, the part that sits in the water. It keeps the ship watertight and forms a strong structure that supports the other parts of the ship and its cargo. Inside the hull are horizontal decks and vertical walls called bulkheads.

The parts of a ship above the main deck are called its superstructure. Most ships have a diesel engine housed low in the hull, which drives a propeller under the stern via a shaft. A rudder at the stern steers the ship. Large ships also have small electrically powered propellers called thrusters for manoeuvring accurately in port.

The SeaCat is a high-speed vehicle ferry. It is a catamaran, which means it has two hulls. Fast ferries like this are powered by gas turbine (jet) engines, giving them top speeds in excess of 40 knots (70 km/h).

Different types of ship have their own specialized parts. For example, vehicle ferries called roll-on roll-off (ro-ro) ferries, designed for a quick turnaround in port, have huge bow or stern doors, and uncluttered decks where the vehicles park. Container ships have their own on-deck cranes for moving containers about. Aircraft carriers have a flat main deck that forms a runway where aircraft take off and land, with hangars underneath.

A giant Nimitz-class aircraft carrier dwarfs a 15th-century carrack. The nuclear-powered Nimitz- class carriers are the world’s largest. They weigh nearly 100,000 tonnes and have a flight deck 333 m long. They provide an operations base for nearly 100 attack aircraft.

Ships are controlled from a room high up near the bow, called a bridge. From here, the crew navigates from place to place, using engine and steering controls, and keeping track of their position using charts, satellite navigation systems, lighthouses and buoys. Radar helps to avoid collisions at night or in fog, and sonar warns of shallow water under the ship.

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STEAMSHIPS

During the nineteenth century, large sailing ships almost completely disappeared as steam power took over. The first successful steam-powered vessel was a river steamer built in the USA by Robert Fulton in 1808. On early steamships the steam engine turned paddle wheels that moved the ship along, but by the 1850s most ships were using propellers instead. Ocean-going steamships kept sails, too, because they could not carry enough coal or water for long-distance voyages, and their engines were not very reliable.

One of the most important sea routes in the nineteenth century was across the Atlantic from Europe to the USA. Millions of people immigrated to the USA in ships. The first regular transatlantic service, starting in 1837, was the wooden paddle-steamer Great Western, built by English engineer Isambard Kingdom Brunel. Larger and larger ships followed, including in 1858 Brunel’s Great Eastern, easily the biggest ship in the world at the time, which could carry 4000 passengers. Both passenger ships and merchant ships continued to increase in size, especially with the introduction of steel hulls in the late nineteenth century.

By the early twentieth century, huge luxury liners were crossing the Atlantic, and steam-powered merchant ships were carrying most of the world’s cargo. The fastest liners used the new steam turbine engine, in which the steam turned a fan-like turbine, which turned the propellers at high speed.

The Grand Princess (launched 1998) is one of the largest of the new generation of cruise liners designed especially for holiday cruising. It is larger than even the biggest of the transatlantic liners. On the ship’s 18 decks there are cabins for 2600 passengers, including luxury suites with balconies, several swimming pools, bars, cafes and a theatre. At the stem is a night club suspended over the ocean.

The Queen Elizabeth was one of the largest and most luxurious liners ever built. It was 314 m long and weighed more than 80,000 tonnes. It entered transatlantic service in 1946 after carrying troops during World War II, and retired in 1968.

In the middle of the twentieth century, steam power began to give way to diesel power. Diesel engines are smaller, cleaner, far more efficient, and need fewer crew to operate them. Steam had almost completely disappeared by the 1980s.

As air travel became convenient and cheap in the 1960s, passengers stopped travelling by sea and the age of the liner came to an end. But as cruise holidays became popular in the 1980s, construction of new, giant cruise liners began.

The French liner Normandie, launched in 1935, was nearly 300 m long, accommodated 1975 passengers and needed 1345 crew. It was the first of what were called the “1000-foot” liners.

HMS Dreadnought, launched in 1906, was the first battleship driven by steam turbines.

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SAILING SHIPS

People made their first journeys across water tens of thousands of years ago. Their first craft must have been logs, used as buoyancy aids. Later, they tied logs together to make rafts, or hollowed them out to make canoes. Where there were no big trees, they made boats from locally available materials, such as reeds or animal skins. Their boats allowed them to travel on rivers and lakes, searching for better fishing, or visiting hunting grounds.

These early craft were propelled by simple paddles, or poles pushed into the river bed. The first sailing boats we know about were built in ancient Egypt in about 3500 BC. Some were built from reeds bundled together, others from wood. They had a single mast with a square sail, which was used in addition to oars when the wind was blowing in a favourable direction. The crew steered with long oars hanging over the stern (rear).

The ancient Greeks and Romans used sturdy, seaworthy cargo boats and sleek fighting boats called galleys, both with a square sail. In battle, the galleys were propelled with oars and attacked enemy ships with a ram on their bows.

About 1000 years ago, the Vikings, who lived in northern Europe, started to explore new lands. Their ships were called knorrs. Each had a hull (body of vessel) made of overlapping or “clinkered” planks.

Chinese boats called junks had sails stiffened by thick bamboo poles, and a sternpost rudder for steering. Until the 15th century they were the world’s biggest and best boats.

The arrangement of sails on a boat is called its rig. A square rig consists of sails hung on a boom across the boat (as in ancient Egyptian and Viking boats). This sort of rig cannot make the best use of wind blowing from side-on. The fore-and-aft rig, with a triangular sail hanging from a boom parallel with the boat’s sides, is more effective. The Chinese had developed a similar rig on their early junks in about 500 BC. It was developed in the Mediterranean in the third century AD. In Europe in the fifteenth century, ships began to appear with a mixture of rigs - square-rigged sails on some masts and fore-and-aft rigs on others. Through the centuries, sailing ships grew larger, with more, taller masts and more sails on each one.

The fastest sailing ships were the “clippers”, which had a huge sail area to take advantage of light winds, and streamlined hulls. They were used to carry important cargoes around the world, such as the new crop of tea from China to Europe.

By the 16th century, small, sturdy ships such as carracks and galleons were capable of long ocean crossings. With the aid of compasses to stop them accidentally sailing in circles, sailors set out from European ports to explore the world and to try to find new sea routes to the Spice Islands of Asia.

Among these explorers was the Portuguese navigator Ferdinand Magellan, who left Spain in 1519 with five ships to sail to Asia around the southern tip of newly-discovered America. Magellan himself was killed in the Philippines, two years into the voyage. Only one of the ships, the Vittoria, under the captaincy of Sebastian del Cano, finally got back to Spain, 1082 days after it left. It was the first ship to circumnavigate the world.

Barques were high-capacity, multi-masted sailing ships that carried bulk cargoes such as grain between Europe, South America and Australia. A small crew could operate the barque’s simple rig. This particular barque, France II, built in 1911, was the biggest sailing ship ever built. Its steel hull was 127 metres long.

MODERN TRAINS

There are three types of modern locomotive - electric, diesel-electric and diesel. On an electric locomotive, the wheels are moved by electric motors (normally one for each pair of wheels). The electricity usually comes from overhead cables, but sometimes from an electrified third rail. On a diesel-electric locomotive, the wheels are also driven by electric motors, but the electricity comes from a generator driven by a powerful diesel engine. On a diesel locomotive, a diesel engine drives the wheels via a mechanical transmission. Diesel locomotives are normally used only for shunting and on low-speed local trains. The fastest express trains, such as the French Train a Grande Vitesse (TGV), are normally electrically powered, with a locomotive at each end.

The TGV runs at 300 kilometres per hour - half as fast again as most express trains - and holds the world-record speed of 515 kilometres per hour. It runs on a purpose-built track, which has few bends, and uses computerized signaling.

The TGV can climb steeper slopes than other trains, allowing its purpose-built track to go straight over hills instead of around them.

Many high-speed expresses run on similar tracks, including the Japanese shinkansen or “bullet” trains, which began operating in 1965. Where purpose-built straight tracks are not possible, speeds can be increased by using tilting trains. These tilt inwards as they go round curves at high speed in the same way as motorcyclists do on the road. Other special trains include magnetic levitation (maglev) trains, which are both supported above their tracks and propelled by magnets. Maglev trains can reach very high speeds because there is no friction between the train and the track.

STEAM TRAINS

A train is a vehicle that runs on guide rails called a railway. Miners have used simple wooden or iron railways called wagon-ways for hundreds of years to move rock, coal and ore in trucks. The trucks were pulled and pushed by animals or the miners themselves. The first locomotive powered by a steam engine was built in 1804 by English engineer Richard Trevithick, to haul trucks at an ironworks. The first passenger railway was the Stockton and Darlington Railway in England, which opened in 1828.

HOW A STEAM LOCOMOTIVE WORKS

A steam locomotive is simply a steam engine on wheels. Fuel burns in the firebox, creating hot gases that pass along tubes inside the boiler. The heat from the tubes boils the water, creating steam. As more steam collects at the top of the boiler, its pressure builds up, and it escapes along pipes to the cylinders, where, controlled by valves, it pushes the pistons one way then the other (this is called double action). The sliding motion of the pistons moves the large driving wheels round via a system of linked connecting rods.

SPREAD OF THE RAILWAYS

Extensive railway networks were developed during the second half of the nineteenth century, especially in the USA, Canada, Europe and Russia. Improvements in tracks, including the introduction of steel rails in the 1860s, allowed for heavier locomotives, with increased power and speed. Carriage design also improved, and dining cars and sleeping cars were introduced by George Pullman in the USA. Railway networks relied on other engineering improvements. Long-span steel bridges carried trains over wide rivers, and rock tunnels took them under mountain ranges such as the Alps. From the 1850s the electric telegraph allowed communications between stations so that signaling staff could keep track of where the trains were.

By the 1930s powerful, streamlined steam locomotives could haul passenger trains at high speeds. But steam locomotives arc very inefficient. Only about five per cent of the energy in the fuel gets to the wheels, and time is needed to start the fire and get the water boiling. In the 1950s and 1960s, steam locomotives disappeared from most railways and were replaced by electric-powered and diesel-powered locomotives. However, steam engines are still used in some countries, such as India and China.

Electric locomotives ran as early as 1879 in Germany. In 1890 they began pulling trains on underground railways in London, and in 1903 on mainline railways in Europe. Diesel locomotives started operating in the USA in the 1930s.

The “Big Boy” locomotives, built in the 1940s for the Union Pacific Railroad in the USA, were the largest (at 40 m long), heaviest (at 600 tonnes) and most powerful steam locomotives of all. But they were not the fastest. That record belongs to the streamlined British locomotive Mallard, which set the world-record speed for a steam locomotive of 201 km/h in 1938. The record still stands today.

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Seaplanes and flying boats have floats instead of wheels, so that they can land on water. In the 1930s, flying boats were often larger and more luxurious than ordinary aircraft, as they could be made larger without the expense of creating longer runways at airports around the world. Instead, they took off and landed at sea, taxiing in and out of existing harbours.

In aviation, a water landing is, in the broadest sense, an aircraft landing on a body of water. Some aircraft such as floatplanes land on water as a matter of course. The phrase “water landing” is also used as a euphemism for crash-landing into water an aircraft not designed for the purpose, an event formally termed ditching. In this case, the flight crew knowingly makes a controlled emergency landing on water. Ditching of commercial aircraft is a rare occurrence.

Seaplanes, flying boats, and amphibious aircraft are designed to take off and alight on water. Alighting can be supported by a hull-shaped fuselage and/or pontoons. The availability of a long effective runway was historically important on lifting size restrictions on aircraft, and their freedom from constructed strips remains useful for transportation to lakes and other remote areas. The ability to loiter on water is also important for marine rescue operations and fire-fighting. One disadvantage of water alighting is that it is dangerous in the presence of waves. Furthermore, the necessary equipment compromises the craft's aerodynamic efficiency and speed.

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Air traffic controllers have screens on which they can see the planes in their sector. It is their job to see that planes are kept safely apart and guided appropriately during take-off and landing. When aeroplanes are near enough, the air traffic controllers can speak to them directly, but they cannot be expected to speak all the languages of international pilots. For this reason, to make communications as safe and clear as possible, all instructions and discussions take place in English all over the world.

Air traffic controllers use an aircraft’s registration mark when calling it by radio. As one letter can sound rather like another, words are used instead, each one standing for the letter that begins it.

Until controller-pilot data link communication (CPDLC) comes into widespread use, air traffic control (ATC) will depend upon voice communications that are affected by various factors. Aircraft operators and air traffic management (ATM) providers, like pilots and controllers, are close partners in terms of “productivity” for enhancing the airport and airspace flow capacity; operators and ATM should also be close partners in terms of “safety” or risk management.

Communication between controllers and pilots can be improved by the mutual understanding of each other’s operating environment. This briefing note provides an overview of various factors that may affect pilot-controller communication. It may be used to develop a company awareness program for enhancing pilot-controller communications.

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Gliders are so light that the lift created by their wings can overcome the opposing pull of gravity. However, without engines, gliders cannot take off. There are two widely used methods of launching gliders into the air. They can be catapulted upwards from the ground, or they can be towed up by an aeroplane. The cable between the plane and the glider is then released, and the glider can fly solo. A glider flight is an extraordinary experience, as it is almost silent except for the sound of the wind.

The wings on a glider have to produce enough lift to balance the weight of the glider. The faster the glider goes the more lift the wings make. If the glider flies fast enough the wings will produce enough lift to keep it in the air. But, the wings and the body of the glider also produce drag, and they produce more drag the faster the glider flies. Since there's no engine on a glider to produce thrust, the glider has to generate speed in some other way. Angling the glider downward, trading altitude for speed, allows the glider to fly fast enough to generate the lift needed to support its weight.

The way you measure the performance of a glider is by its glide ratio. This ratio tells you how much horizontal distance a glider can travel compared to the altitude it has to drop. Modern gliders can have glide ratios better than 60:1. This means they can glide for 60 miles if they start at an altitude of one mile. For comparison, a commercial jetliner might have glide ratios somewhere around 17:1.

If the glide ratio were the only factor involved, gliders would not be able to stay in the air nearly as long as they do. So how do they do it?

The key to staying in the air for longer periods of time is to get some help from Mother Nature whenever possible. While a glider will slowly descend with respect to the air around it, what if the air around it was moving upward faster than the glider was descending? It's kind of like trying to paddle a kayak upstream; even though you may be cutting through the water at a respectable pace, you're not really making any progress with respect to the riverbank. The same thing works with gliders. If you are descending at one meter per second, but the air around the plane is rising at two meters per second, you're actually gaining altitude.

Newton’s third law of motion states that, for every action, there is an equal and opposite reaction. Based on this law, wings are forced upwards because they are tilted, pushing air downwards so the wings get pushed upwards. This is the angle of attack or the angle at which the wing meets the airflow.

As air flows over the surface of a wing, it sticks slightly to the surface it is flowing past and follows the shape. If the wing is angled correctly, the air is deflected downwards. The action of the wing on the air is to force the air downwards while the reaction is the air pushing the wing upwards. A wing’s trailing edge must be sharp, and it must be aimed diagonally downwards to create lift. Both the upper and lower surfaces of the wing act to deflect the air.

The amount of lift depends on the speed of the air around the wing and the density of the air. To produce more lift, the object must speed up and/or increase the angle of attack of the wing (by pushing the aircraft’s tail downwards).

Speeding up means the wings force more air downwards so lift is increased. Increasing the angle of attack means the air flowing over the top is turned downwards even more and the air meeting the lower surface is also deflected downwards more, increasing lift. There is a limit to how large the angle of attack may be. If it is too great, the flow of air over the top of the wing will no longer be smooth and the lift suddenly decreases.

Birds and planes change their angle of attack as they slow to land. Their angle of attack is increased to ensure their lift continues to support their weight as they slow down. Wings and tails need to be movable so that their shapes can be changed to control their flight.

Helicopters have rotor blades above them that are aerofoils. When they turn rapidly, they create lift. The blades are tilted slightly, so that they also provide thrust. The helicopter’s tail rotor blades stop the helicopter from spinning and enable it to turn. With this combination of rotors, a helicopter can move in any direction or simply hover. Without long wings, helicopters can manoeuvre in tight places, such as alongside cliff faces, so they are particularly useful for rescue and emergency work.

The science of a helicopter is exactly the same as the science of an airplane: it works by generating lift—an upward-pushing force that overcomes its weight and sweeps it into the air. Planes make lift with airfoils (wings that have a curved cross-section). As they shoot forwards, their wings change the pressure and direction of the oncoming air, forcing it down behind them and powering them up into the sky: a plane's engines speed it forward, while its wings fling it up. The big problem with a plane is that lots of air has to race across its wings to generate enough lift; that means it needs large wings, it has to fly fast, and it needs a long runway for takeoff and landing.

Helicopters also make air move over airfoils to generate lift, but instead of having their airfoils in a single fixed wing, they have them built into their rotor blades, which spin around at high speed (roughly 500 RPM, revolutions per minute). The rotors are like thin wings, "running" on the spot, generating a massive downdraft of air that blows the helicopter upward. With skillful piloting, a helicopter can take off or land vertically, hover or spin on the spot, or drift gently in any direction—and you can't do any of that in a conventional plane.

Aeroplanes fly when two of the four forces acting upon them are greater than the other two. The force of thrust, created by the aeroplanes propellers or jet engines, moves the plane forward. The force of lift is caused by air flowing over the wings. This keeps the plane in the air. The two forces working against thrust and lift are gravity, which pulls the plane towards the Earth, and drag, caused by air resistance, which slows the plane’s forward motion.

Four forces act on a plane in flight. When the plane flies horizontally at a steady speed, lift from the wings exactly balances the plane's weight and the thrust exactly balances the drag. However, during takeoff, or when the plane is attempting to climb in the sky, the thrust from the engines pushing the plane forward exceeds the drag (air resistance) pulling it back. This creates a lift force, greater than the plane's weight, which powers the plane higher into the sky.

If you've ever watched a jet plane taking off or coming in to land, the first thing you'll have noticed is the noise of the engines. Jet engines, which are long metal tubes burning a continuous rush of fuel and air, are far noisier (and far more powerful) than traditional propeller engines. You might think engines are the key to making a plane fly, but you'd be wrong. Things can fly quite happily without engines, as gliders (planes with no engines), paper planes, and indeed gliding birds readily show us.

Newton's third law of motion explains how the engines and wings work together to make a plane move through the sky. The force of the hot exhaust gas shooting backward from the jet engine pushes the plane forward. That creates a moving current of air over the wings. The wings force the air downward and that pushes the plane upward.

Beneath cities are the foundations of large buildings and many pipes carrying water, electricity, gas and telephone cables. Builders have either to tunnel very deeply or to use a technique called “cut-and-cover”, which means that they run the railway under existing roads, so that they simply have to dig a huge trench along the road, build the railway, and cover it up again.

The building method used for many years was a so-called “cut-and-cover” system. It was easier to dig out a large open hole in the road, build the arch of the false tunnel with bricks, and then refill the hole with the dug-out material. As a result, the first underground lines were not very deep, something that tends to be the case with the older underground lines in major cities.

One of the companies of the time, C&SLR, was the first to use electric traction for pulling the trains, as well as a new method for digging circular tunnels, using a technology known as “shield tunneler”, which initially was opearated manually. The front part was used to dig out a circular section and the tunneling machine was called the Greathead Shield. Later on, the shield became mechanical and the machine advanced much more rapidly and could cut through any type of material. Today, these are called TBMs, or Tunnel Boring Machines.

These tunnelling machines made it possible to dig under the city at a greater depth and create new underground lines on another level: they could dig under buildings and keep away from electricity lines, sewers and other infrastructures. They could even dig under the Thames.

Fast forward 155 years to our times. A massive new rail undertaking spanning over 100 km, more than 40 km of which run below the streets of London, connecting with the underground network at some points.

The world’s first city underground railway line was opened in 1863 in London. It was called the Metropolitan. The London Underground (also known simply as the Underground or by its nickname the Tube) is a public rapid transit system serving London region, England and some parts of the adjacent counties of Buckinghamshire, Essex and Hertfordshire in the United Kingdom.

The Underground has its origins in the Metropolitan Railway, the world's first underground passenger railway. Opened in January 1863, it is now part of the Circle, Hammersmith & City and Metropolitan lines; the first line to operate underground electric traction trains, the City & South London Railway in 1890, is now part of the Northern line. The network has expanded to 11 lines, and in 2017/18 carried 1.357 billion passengers, making it the world's 12th busiest metro system. The 11 lines collectively handle up to 5 million passengers a day.

The system's first tunnels were built just below the ground, using the cut-and-cover method; later, smaller, roughly circular tunnels—which gave rise to its nickname, the Tube—were dug through at a deeper level. The system has 270 stations and 250 miles (400 km) of track. Despite its name, only 45% of the system is underground in tunnels, with much of the network in the outer environs of London being on the surface. In addition, the Underground does not cover most southern parts of London region, and there are only 29 stations south of the River Thames.