What makes a Bullet Train so fast?

The main different options for planes are feet, autos, transports, watercrafts and routine prepares however they are just too moderate for today's quick paced society. Notwithstanding, there is another type of transportation that could alter transportation of the 21st century the way planes did in the 20th century that are the Bullet trains or the Maglev trains. Maglev trains got their name from their operating principle that is magnetic levitation.

Principle of Operation

Magnetic levitation means that the train is rose from the ground using magnets. No overhead power cables because the power source is built into the track. There’s no friction from the wheels because there aren’t any wheels! The train is suspended on a magnetic cushion above a magnetized track and so travel free of friction. Trains are designed to float 100 mm above the track so the only resistance it has is air resistance which makes the train very fast,

Working

Maglev trains are all about magnets and magnets have a south and north pole. When magnets of same poles are brought face to face they repel. The Japanese maglev trains use this repulsion to lift themselves on the track. Hence the train rests on the repulsive force as if it’s sitting on an invisible cushion. Speed reached is approx. 590 km per hour. This technology has been confined only to test tracks. While the German Maglev trains use the attractive force of the magnets. But there’s no use of a train sticking to its track. So the trick to hover the train on the tracks is use of electromagnets

(Electromagnet- It is a coil of wire through which electricity passes causing a magnetic field to be produced. No friction as the train hovers above the ground)

If electromagnets are switched on and off very rapidly, we can defeat gravity attracting and dropping so quickly that a metal objects will hover. There are massive electromagnets that sit under the track and when the power is switched on, the magnets are attracted to the track causing the whole train to float 10 mm above the track.

A separate system of magnets which are called the guide magnets is built into the track to create a moving magnetic field that pushes the train along with it and this makes the system very effective. Hence guide magnets control propulsion. The vehicle is propelled by interaction of magnetic forces between its on board magnets and the magnetic coils on the sides of the guide way. So for the train to move the tracks need to be energized by just switching on the power.

The magnetized coil running along the track, called a guide way, repels the large magnets on the train's undercarriage, allowing the train to levitate above the guide way. Once the train is levitated, power is supplied to the coils within the guide way walls to create a unique system of magnetic fields that pull and push the train along the guide way. The electric current supplied to the coils in the guide way walls is constantly alternating to change the polarity of the magnetized coils. This change in polarity causes the magnetic field in front of the train to pull the vehicle forward, while the magnetic field behind the train adds more forward thrust.

How does it stop?

Maglev train doesn't have any wheels or break shoes as there is no friction at all and no connection with the ground. So to slow down or to stop the train the current is flown in the reversed direction or in the opposite direction, which causes retardation in the speed of the train and eventually brings it to rest.

Engineers are working to improve the maglev system to make the trains run a lot faster at a jaw dropping speed of 3500 km per hour.  This has been made possible in theory by making the train run on vacuum sheets. According to the theory the time required to reach Tokyo from London will be 3 and a half hours. 50 million euros per mile is an investment required to put a maglev system where the cost of manufacturing for the train is different. Hence it is a very costly affair for the government to look into! 

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How does a rocket work?

Law Of Conservation of Momentum

The basic principle that all rockets work by is law of conservation of momentum that is the total momentum of two objects before collision is equal to the total momentum of the two objects after collision that is the momentum lost by object 1 is equal to the momentum gained by object two.

In case of rocket science the rocket launches itself by ejecting some of its mass downwards. In fact while a rocket is being accelerated upwards its engine is continuously ejecting some mass and forcing it downwards. Because this mass is forced downwards, by conservation of momentum the rocket must then be forced upwards. In terms of forces the rocket has to exert some force on the ejected mass to push it downwards which then results in an equal and opposite reaction force pushing the rocket. Greater is the momentum, more is the thrust developed. That is how law of conservation of momentum or Newton’s third law of motion is responsible for launching of rocket.

Types of Propulsion System

There are only two types of propulsion system which can get a rocket escape the earth’s atmosphere. They are   i.) Liquid Propellant Rocket Engine  ii.)Solid Propellant Rocket Engine

In this article we will understand about how a liquid propellant rocket engine works.

Inside the rocket engine we have the combustion chamber, the throat and the nozzle. Inside the combustion chamber the fuel and the oxidizer mix. The liquid fuel before entering the combustion chamber travels through the nozzle body as it helps to reduce nozzle cover temperature and also covers some energy savings. To pump the fuel and the oxidizer in adequate rate, two pumps are used. These pumps are driven by a turbine which is connected to the same shaft as the pumps. The pump turbine unit is referred to as turbo pump. A gas generator produces hot gas to rotate the turbine. The gas generator uses bypassed fuel and bypassed oxidizer for the purpose of combustion. Exhaust from the turbine is mixed with main rocket exhaust.

Even as the liquid fuel converts into gas, the mass of the fuel remain the same. The massive acceleration of this transformation from liquid to gas causes the momentum. The mathematical representation of this energy transformation is  E=MV² (m=mass of gas, v=velocity of gas) which implies faster is the velocity of the gases more is the energy released. Lighter is the fuel better is it as lighter fuels can move faster. Hence the engine uses the mass and the velocity of the fuel as it burns to create thrust.

For example heavier but slower fuel mixture like kerosene and liquid oxygen won’t give as much energy as mixture of liquid hydrogen and liquid oxygen. The engine’s efficiency can increase by adjusting the hydrogen and oxygen ratio by making it more hydrogen rich. So we conclude that if we can take a really light fuel moving at very high velocity, we end up creating more efficient rockets

To make it to the exosphere (space)

The fuel and the oxidizer required for the rocket engine are stored in two large tanks. During lift off the thrust produced by the main engine may not be sufficient so usually a few solid propellant strap boosters are used to assist the lift off. The solid propellant strap boosters get burned off rapidly so to reduce the weight they are abandoned after the burn off. Now the next engine takes the charge. This way the rocket’s weight is greatly reduced. Hence great acceleration can be achieved. This process is called staging.

After the rocket has reached the desired height the rocket’s nozzle is slightly tilted by high precision devices. Hence the rocket will turn to the desired angle. After the angle is made the nozzle comes back to its original position. Now the second engine is ignited to give the rocket enough inertia to reach its desired destination.

  

Liquid Propellant Engines have high specific thrust where thrust can be controlled and can be restarted. 

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Western World’s Largest Submarine: The USS Pennsylvania.

Submarine is a watercraft which propels beneath the water as well as on the water while a ship can travel only on water. Submarines are used in the navy, usually built for warfare and for marine research. Submarines are highly efficient than ships. A submarine or ship floats due to the buoyant force which acts just opposite gravity. However, a submarine is also able to control its buoyancy, and therefore it is able to sink or float on surface on its own will.

The difference between a surface ship and a submarine is that a surface ship generally tries to keep the water out in order to stay buoyant, while a submarine has ballast tanks that are designed to be flooded when required to sink and to have the water pushed out of it when the submarine wishes to rise towards the surface

In 1954 the first nuclear powered submarine, USS Nautilus was launched which was a prototype. Nautilus was decommissioned in 1980 and designated a National Historic Landmark in 1982. The USS Pennsylvania is also a nuclear powered submarine but the submarine’s nuclear reactor is far more powerful. It generates more than enough electricity to propel 17000 ton USS Pennsylvania at 45km/hour as compared to Nautilus’s speed of 7.6 km/hour. The Electric Boat Division of Groton started building the USS Pennsylvania in the year 1982 and completed it by the year 1984. It sank in the year 1988 and got commissioned in the year 1989.

The USS Pennsylvania is 172 meters in length, 12.8 meters wide and 11.1 meters in height. Its weight when surfaced is approximately 16,765 tons and 18,750 tons when submerged. The crew comprises of 17 officers, 15 Chief Petty Officers and 122 crewmen. It has the capacity to carry food supplies for the entire crew for 3 months.

Where does it get its power from?

The USS Pennsylvania uses a nuclear reactor that breaks uranium which triggers a massive release of heat. This heat is used to generate steam to rotate turbines at high speed which then drives the propellers but the nuclear reactor is enormous in size and to accommodate it, the submarine also has to be vast. It can travel 100,000 km for 4kg of uranium. So it doesn’t need to be refueled at sea.

How do the crewmen breathe inside the submarine?

Each crewman requires 12 cc air every day to stay alive and more if working hard. This way air will get over in seven days in a normal submarine. To overcome this problem air is made in the submarine itself in the oxygen generator from sea water by electrolysis by passing electric current into sea water

to split hydrogen and oxygen. Four thousand liters of oxygen is circulated through pipes throughout the vessel every hour.

How is it helpful during the war?

Submarine USS Pennsylvania contains advanced torpedoes that are like high tech robots that can be guided on to their target.  An optic fiber spooning out of the torpedo connects the torpedo to the submarine to obey the officer’s command to guide it on to the target. As the torpedo closes in, it’s on board sensors lock on and hit the target.  Torpedoes are powerful enough to sink an entire ship or a submarine.

Russians launched the first rocket atom bomb. The submarine had to first surface the water as rocket engines needed air to burn so they don’t work under water. But a submarine surfaced on water could be easily air bombed so the Americans wanted to design a rocket atom bomb that could be launched without surfacing the submarine on water. This is how they did it-

The rocket has a seal which doesn’t allow water to enter. When rocket has to be launched, the seal breaks moment before launch but before water could enter the hatch a valve opens from which compressed air gushes into the hatch pushing the rocket out with 80km/hour which has enough momentum to cut 40 meters of water. Once the rocket comes out of the water, the rocket engine ignites and the rocket travels on its further trajectory.

How does it prevent itself from getting detected?

Light can penetrate into the sea only till a few meters but sound can travel for hundreds of kilometers so noise needs to be reduced. All the machines and the fits inside the submarine are attached with sound insulators. Most of the noise comes from the propellers. When the propellers rotate quickly, area of low pressure is created near the blades and hence the temperature increases therefore leading to the formation of steam bubbles. This process is called cavitation so the faster the submarine propels more is the cavitation and therefore noise. When these bubbles pop, they make noise. But to lower the noise propellers need to be rotated at low speed but this will also reduce the thrust which will disturb the submarine’s movement. To overcome this problem the propeller has special types of blade which even at low speeds generate enough thrust.

The USS Pennsylvania is still in active service, as of 2015 somewhere in the ocean maybe right beneath your boat.

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Ever wondered how does a submarine works? Click here to find out!

A submarine has a sleek cigar shaped body which enables it to move swiftly under water. The submarine contains a pressure hall made up of high strength metal. It contains submarine’ crew machinery and most or all weapons preventing them from getting crushed by the pressure of water when the submarine is under deep depths. A submarine has ballast tanks which are surrounding the pressure hall. The ballast tanks control the buoyancy of the submarine.  

Pressure hall is water tight and air tight and is strong enough to withstand the pressure of the water. The pressure hall is divided into different compartments by water tight bulk heads with water tight doors. These departments include the control room for diving, steering and operating when submerged. The conning tower is above the control room which contains the periscope.

It also includes the pump room, room for storing food and other supplies, battery space, office quarters, crew quarters, sonar rooms, engine rooms, maneuvering rooms for electrical control systems and the torpedo rooms.

To make the submarine dive, the main ballast tanks are flooded with sea water. The additional weight causes the ship to lose the ability to stay on the surface of water.

To resurface the water is blown out of the ballast tanks by compressed air so that the submarine comes up to the water.

Fore planes and side planes are used for steering. Angle of submarine is controlled by tail planes. The propeller generates the thrust to move the submarine forward and backward. It is either engine or nuclear powered. 

Submarines are used in the navy and for sea research.

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How to drown a ship? Fire a torpedo!

The concept of a torpedo existed many centuries before it was developed as a working device. A possible early description is found in the works of Syrian engineer Hassan al-Rammah in 1275, who described, "...an egg which moves itself and burns. Though, torpedos came into use after the mid-19^th century. Torpedos have evolved since the 19^th century into extremely effective undersea weapons.

A torpedo has a propulsion system, a guidance system and some sort of explosive device. Torpedoes can travel several miles on their way to the target, and therefore they need a propulsion system that can run for 10 to 20 minutes. In this article we will know how the earlier torpedos as well as the modern torpedos work.

  

1.)    Torpedo propels itself powered by tank of compressed air

2.)    On launch a valve opens and the air is released into the engine which contains two pistons. Their motion drives a propeller which pushes the torpedos for the water

But the air propelled torpedo consists of a major flaw the compressed air that leaves the torpedo leaves a trail of bubbles which eventually come on the surface and makes their path of travel visible which can be easily traced. So it was in during the World War II when the German Navy designed a torpedo that didn’t advertise its position with the wake of bubbles. The torpedo which was designed didn’t run on compressed air but worked with the help of an electric motor that ran on an enormous battery. But to accommodate the battery the torpedo were needed to be at least 7 meters long.

Today USS Pennsylvania submarine contains advanced torpedos that are like high tech robots that can be guided on to their target.  An optic fiber spooning out of the torpedo connects the torpedo to the submarine to obey the officer’s command to guide it on to the target. As the torpedo closes in, it’s on board sensors lock on and hit the target.  Torpedos are powerful enough to sink an entire ship or a submarine.

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How does a 4 stroke diesel engine works?

How does a 4 stroke diesel engine works?

In the previous article we read about how a 4 stroke petrol engine works. In this article we will know the difference between the working of the petrol and the diesel engine. When we talk about diesel engine the spark plug is absent and a fuel injector is present inside the cylinder block.

The four stroke diesel engine working comprises of the same four strokes as that of the petrol engine but some part of it is very different.

  

A diesel engine is based on the principle of Diesel cycle. It can be either 2 stroke or 4 stroke. In this article we will see how the 4 stroke diesel engine works.

1.)    Suction Stroke

2.)    Compression Stroke

3.)    Power Stroke

4.)    Exhaust Stroke

The main important parts of the engine are the piston, the crankshaft, the connecting rod and the cylinder block which includes the cylinder head. The cylinder head comprises of the rocker arm and spring mechanism which with the help of a cam controls the opening and closing of the inlet valve and exhaust valve. The cylinder block is surrounded by water jackets which helps cooling of the cylinder block. The parts of the cylinder are shown below.

Suction Stroke (same as that of petrol engine)

The first stroke is suction stroke. In this stroke, the

 piston moves from TDC (Top Dead Centre) to the BDC( Bottom Dead Centre), which are the two extreme most positions of the piston. When the piston moves from TDC to BDC the inlet valve opens through which fresh charge (atmospheric air + petrol) is sucked in.

Compression Stroke (same as that of petrol engine but higher temperature-pressure)

The second stroke is the compression stroke in which the piston moves from BDC to TDC. When the piston moves from BDC to TDC the inlet valve closes and the charge is compressed thereby increasing its temperature. When compared to petrol engine the temperature and pressure developed inside the cylinder block is much higher. To withstand the high temperature-pressure the diesel engine is bulky and heavier than petrol engine.  

Power Stroke

The third stroke is the power stroke which is the most important stroke in which the piston moves from TDC to BDC. After the compression stroke the piston is at TDC and this when fuel injector injects or sprays diesel inside the cylinder block and the temperature-pressure inside the cylinder block has already risen to great extent during compression which is enough to ignite the fuel (no need of spark plug). Hence combustion takes place inside the cylinder block and displaces the piston from TDC to BDC. The main power of the engine is generated from this stroke. Some amount of power is stored the flywheel to execute the other three strokes and the rest of the power is used to drive the wheels of the car. The inlet and the exhaust valves remain closed.

Exhaust Stroke (same as that of petrol engine)

The fourth stroke is the exhaust stroke in which the piston moves from BDC to TDC. The hot gases 

and the fumes which are generated from combustion of the charge are pushed out through the exhaust valve which opens when the piston moves from BDC to TDC.  

The Diesel Cycle graph is shown as follows

Constant Pressure Process: Heat is rejected and received at constant pressure.

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How does a 4 stroke petrol engine works?

How does a 4 stroke petrol engine works?

An engine, or motor, is a machine designed to convert one form of energy into mechanical energy. Heat engines, including internal combustion engines and external combustion engines (such as steam engines) burn a fuel to create heat, which then creates a force. In simpler words an engine is a machine with moving parts that convert power into motion. It can be broadly classified:

According to the type of cycle

i.)                  Otto Cycle (Air Cycle)

ii.)                 Diesel Cycle

iii.)               Dual Cycle

According to the alignment of cylinders

i.)                  In Line type

ii.)                 V type

iii.)               Rotary type

According to the speed

i.)                  Low speed

ii.)                 Medium Speed

iii.)               High Speed

According to the type of ignition

i.)                  Spark ignition

ii.)                 Combustion ignition

According to the type of fuel used

i.)                  Petrol

ii.)                 Diesel

According to the number of strokes

i.)                  2 Stroke

ii.)                 4 Stroke

There are few more types.

In this post we will understand about how a petrol engine works. A petrol engine is based on the principle of Otto cycle (Air Cycle). It can be either 2 stroke or 4 stroke. In this articlewe will see how the 4 stroke petrol engine works.

1.)    Suction Stroke

2.)    Compression Stroke

3.)    Power Stroke

4.)    Exhaust Stroke

The main important parts of the engine are the piston, the crankshaft, the connecting rod and the cylinder block which includes the cylinder head. The cylinder head comprises of the rocker arm and spring mechanism which with the help of a cam controls the opening and closing of the inlet valve and exhaust valve. The cylinder block is surrounded by water jackets which helps for cooling of the cylinder block. The parts of the cylinder are shown below.

Suction Stroke

The first stroke is suction stroke. In this stroke, the piston moves from TDC (Top Dead Centre) to the BDC( Bottom Dead Centre), which are the two extreme most positions of the piston. When the piston moves from TDC to BDC the inlet valve opens through which fresh charge (atmospheric air + petrol) is sucked in.

Compression Stroke

The second stroke is the compression stroke in which the piston moves from BDC to TDC. When the piston moves from BDC to TDC the inlet valve closes and the charge is compressed thereby increasing its temperature.  

Power Stroke

The third stroke is the power stroke which is the most important stroke in which the piston moves from TDC to BDC. When the piston is at TDC the spark plug makes a spark inside the cylinder block thereby igniting the charge hence combustion takes place inside the cylinder block and displaces the piston from TDC to BDC. The main power of the engine is generated from this stroke. Some amount of power is stored the flywheel to execute the other three strokes and the rest of the power is used to drive the wheels of the car. The inlet and the exhaust valves remain closed.

Exhaust Stroke

The fourth stroke is the exhaust stroke in which the piston moves from BDC to TDC. The hot gases and the fumes which are generated from combustion of the charge are pushed out through the exhaust valve which opens when the piston moves from BDC to TDC.   

The Otto Cycle graph is shown as follows

Constant Volume Process: Heat is rejected and received at constant volume.

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