Physics. Jet propulsion in nature and technology. Interesting information about jet propulsion Where does jet propulsion occur in nature

Multi-ton spaceships soar into the sky, and transparent, gelatinous jellyfish, cuttlefish and octopuses deftly maneuver in the sea waters - what do they have in common? It turns out that in both cases, the principle of jet propulsion is used to move. It is this topic that our today's article is devoted to.

Let's look into history

Most The first reliable information about rockets dates back to the 13th century. They were used by Indians, Chinese, Arabs and Europeans in combat operations as military and signal weapons. Then followed centuries of almost complete oblivion of these devices.

In Russia, the idea of ​​using a jet engine was revived thanks to the work of the Narodnaya Volya revolutionary Nikolai Kibalchich. Sitting in the royal dungeons, he developed Russian project jet engine and aircraft for people. Kibalchich was executed, and for many years his project was gathering dust in the archives of the tsarist secret police.

The main ideas, drawings and calculations of this talented and courageous person received further development in the works of K. E. Tsiolkovsky, who proposed using them for interplanetary communications. From 1903 to 1914, he published a number of works, where he convincingly proves the possibility of using jet propulsion to explore outer space and substantiates the feasibility of using multi-stage rockets.

Many scientific developments of Tsiolkovsky are still used in rocket science.

biological missiles

How did it come about the idea of ​​moving by pushing off your own jet stream? Perhaps, closely watching the marine life, the inhabitants of the coastal zones noticed how this happens in the animal world.

For instance, scallop moves due to the reactive force of the water jet ejected from the shell during the rapid compression of its valves. But he will never keep up with the fastest swimmers - squids.

Their rocket-shaped bodies rush tail forward, throwing out stored water from a special funnel. move according to the same principle, squeezing out water by contracting their transparent dome.

Nature endowed a "jet engine" and a plant called "squirting cucumber". When its fruits are fully ripe, in response to the slightest touch, it shoots out gluten with seeds. The fetus itself is thrown in the opposite direction at a distance of up to 12 m!

Neither marine life nor plants know the physical laws underlying this mode of locomotion. We'll try to figure this out.

Physical foundations of the principle of jet propulsion

Let's start with a simple experiment. Inflate a rubber ball and, without tying, we will let go into free flight. The rapid movement of the ball will continue as long as the stream of air flowing from it is strong enough.

To explain the results of this experience, we should turn to the third law, which states that two bodies interact with forces equal in magnitude and opposite in direction. Therefore, the force with which the ball acts on the jets of air escaping from it is equal to the force with which the air repels the ball from itself.

Let's transfer this reasoning to the rocket. These devices at great speed throw out some of their mass, as a result of which they themselves receive acceleration in the opposite direction.

From a physics point of view, this the process is clearly explained by the law of conservation of momentum. Momentum is the product of the body's mass and its velocity (mv) While the rocket is at rest, its velocity and momentum are zero. If a jet stream is ejected from it, then the remaining part, according to the law of conservation of momentum, must acquire such a speed that the total momentum is still equal to zero.

Let's look at the formulas:

m g v g + m p v p =0;

m g v g \u003d - m p v p,

where m g v g the momentum created by the jet of gases, m p v p the momentum received by the rocket.

The minus sign shows that the direction of movement of the rocket and the jet stream are opposite.

The device and principle of operation of a jet engine

In technology, jet engines propel aircraft, rockets, and put spacecraft into orbit. Depending on the purpose, they have a different device. But each of them has a supply of fuel, a chamber for its combustion and a nozzle that accelerates the jet stream.

The interplanetary automatic stations are also equipped with an instrument compartment and cabins with a life support system for astronauts.

Modern space rockets are complex, multi-stage aircraft that use the latest achievements in engineering. After launch, the fuel in the lower stage burns first, after which it separates from the rocket, reducing its total mass and increasing its speed.

Then the fuel is consumed in the second stage, and so on. Finally, the aircraft is brought to a given trajectory and begins its independent flight.

Let's dream a little

The great dreamer and scientist K. E. Tsiolkovsky gave future generations the confidence that jet engines will allow humanity to break out of the earth's atmosphere and rush into space. His prediction came true. The moon, and even distant comets, are successfully explored by spacecraft.

In astronautics, liquid propellant engines are used. Using petroleum products as fuel, but the speeds that can be obtained with their help are insufficient for very long flights.

Perhaps you, our dear readers, will witness the flights of earthlings to other galaxies on vehicles with nuclear, thermonuclear or ion jet engines.

If this message was useful to you, I would be glad to see you

The law of conservation of momentum is of great importance when considering jet propulsion.
Under jet propulsion understand the movement of a body that occurs when a certain part of it is separated at a certain speed relative to it, for example, when combustion products flow out of the nozzle of a jet aircraft. This gives rise to the so-called Reactive force pushing the body.
The peculiarity of the reactive force is that it arises as a result of the interaction between the parts of the system itself without any interaction with external bodies.
While the force imparting acceleration, for example, to a pedestrian, a ship or an airplane, arises only due to the interaction of these bodies with earth, water or air.

So the motion of the body can be obtained as a result of the outflow of a jet of liquid or gas.

In nature, jet propulsion inherent mainly in living organisms living in the aquatic environment.

In technology, jet propulsion is used in river transport (jet engines), in the automotive industry (racing cars), in military affairs, in aviation and astronautics.
All modern high-speed aircraft are equipped with jet engines, because. they are able to provide the required flight speed.
In outer space, it is impossible to use other engines, except for jet engines, since there is no support, starting from which one could get acceleration.

History of the development of jet technology

The creator of the Russian combat missile was the artillery scientist K.I. Konstantinov. With a weight of 80 kg, the range of the Konstantinov rocket reached 4 km.

The idea of ​​using jet propulsion in an aircraft, the project of a jet aeronautical instrument, was put forward in 1881 by N.I. Kibalchich.

In 1903, the famous physicist K.E. Tsiolkovsky proved the possibility of flight in interplanetary space and developed the project of the first rocket plane with a liquid-propellant engine.

K.E. Tsiolkovsky designed a space rocket train, made up of a number of rockets that work in turn and fall off as fuel is used up.

Principles for the use of jet engines

The basis of any jet engine is the combustion chamber, in which, during the combustion of fuel, gases are formed that have a very high temperature and exert pressure on the walls of the chamber. Gases escape from the narrow nozzle of the rocket at high speed and create jet thrust. According to the law of conservation of momentum, the rocket gains speed in the opposite direction.

The momentum of the system (rocket-combustion products) remains equal to zero. Since the mass of the rocket is decreasing, even at a constant speed of outflow of gases, its speed will increase, gradually reaching its maximum value.
Rocket motion is an example of the motion of a body with a variable mass. To calculate its speed, the law of conservation of momentum is used.

Jet engines are divided into rocket engines and jet engines.

rocket engines available in solid or liquid fuels.
In solid propellant rocket engines, a propellant containing both fuel and an oxidizer will be placed inside the combustion chamber of the engine.
V liquid-propellant engines, designed to launch spacecraft, fuel and oxidizer are stored separately in special tanks and pumped into the combustion chamber. Kerosene, gasoline, alcohol, liquid hydrogen, etc. can be used as fuel in them, and liquid oxygen can be used as an oxidizing agent necessary for combustion. nitric acid, and etc.

Modern three-stage space rockets are launched vertically, and after passing through the dense layers of the atmosphere, they are transferred to a flight in a given direction. Each rocket stage has its own fuel tank and oxidizer tank, as well as its own jet engine. As the fuel burns, the spent rocket stages are discarded.

Air jet engines currently used mainly in aircraft. Their main difference from rocket engines is that the oxidizer for fuel combustion is the oxygen of the air entering the engine from the atmosphere.
Jet engines include turbocompressor engines with both axial and centrifugal compressors.
The air in such engines is sucked in and compressed by a compressor driven by a gas turbine. The gases leaving the combustion chamber create a thrust force and rotate the turbine rotor.

At very high flight speeds, the compression of gases in the combustion chamber can be carried out due to the oncoming air flow. The need for a compressor is eliminated.

Completed:
Student
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Okuneva Alena
Checked:
P.L. Vineaminovna

City Perevoz
2011
Content:

Introduction: what is Jet propulsion………………………………………………………… …..…………………………………..3
Law of conservation of momentum…………………………………………………………………….4
Application of jet propulsion in nature…………………………..….…....5
The use of jet propulsion in technology…….…………………...…..….….6
Jet propulsion "Intercontinental missile"…………..………...…7
The physical basis of the jet engine..................... .................... 8
Classification of jet engines and features of their use……………………………………………………………………….………….…….9
Features of the design and creation of an aircraft…..…10
Conclusion……………………………………………………………………………………………….11
List of used literature…………………………………………………………..12

"Jet propulsion"
Jet motion - the movement of a body due to the separation from it with a certain speed of some part of it. Jet motion is described based on the law of conservation of momentum.
Jet propulsion, which is now used in airplanes, rockets and space projectiles, is characteristic of octopuses, squids, cuttlefish, jellyfish - all of them, without exception, use the reaction (recoil) of an ejected jet of water to swim.
Examples of jet propulsion can also be found in the plant world.
In southern countries, a plant called "mad cucumber" grows. One has only to lightly touch the ripe fruit, similar to a cucumber, as it bounces off the stalk, and through the hole formed from the fruit, liquid with seeds flies out at a speed of up to 10 m / s.

The cucumbers themselves fly off in the opposite direction. Shoots a mad cucumber (otherwise it is called a "lady's pistol") more than 12 m.

"Law of Conservation of Momentum"
In a closed system, the vector sum of the impulses of all bodies included in the system remains constant for any interactions of the bodies of this system with each other.
This fundamental law of nature is called the law of conservation of momentum. It is a consequence of Newton's second and third laws. Consider two interacting bodies that are part of a closed system.
The interaction forces between these bodies will be denoted by and According to Newton's third law If these bodies interact during time t, then the impulses of the interaction forces are identical in absolute value and directed in opposite directions: Let's apply Newton's second law to these bodies:

"Application of jet propulsion in nature"
Jet propulsion is used by many mollusks - octopuses, squids, cuttlefish. For example, a sea scallop mollusk moves forward due to the reactive force of a jet of water ejected from the shell during a sharp compression of its valves.

Octopus
The cuttlefish, like most cephalopods, moves in the water in the following way. She takes water into the gill cavity through a lateral slit and a special funnel in front of the body, and then vigorously throws a stream of water through the funnel. The cuttlefish directs the funnel tube to the side or back and, rapidly squeezing water out of it, can move in different directions.
Salpa is a marine animal with a transparent body; when moving, it receives water through the front opening, and the water enters a wide cavity, inside which gills are stretched diagonally. As soon as the animal takes a large sip of water, the hole closes. Then the longitudinal and transverse muscles of the salpa contract, the whole body contracts, and water is pushed out through the rear opening. The reaction of the outflowing jet pushes the salpa forward. Of greatest interest is the squid jet engine. Squid is the largest invertebrate inhabitant of the ocean depths. Squids have reached the highest level of excellence in jet navigation. They even have a body that copies a rocket with its external forms. Knowing the law of conservation of momentum, you can change your own speed of movement in open space. If you are in a boat and you have some heavy rocks, then throwing rocks in a certain direction will move you in the opposite direction. The same will happen in outer space, but jet engines are used for this.

"Application of jet propulsion in technology"
At the end of the first millennium AD, China invented jet propulsion that powered rockets - bamboo tubes filled with gunpowder, they were also used as fun. One of the first car designs was also with a jet engine and this project belonged to Newton.
The author of the world's first project of a jet aircraft designed for human flight was the Russian revolutionary N.I. Kibalchich. He was executed on April 3, 1881 for participating in the assassination attempt on Emperor Alexander II. He developed his project in prison after the death sentence. Kibalchich wrote: “While in prison, a few days before my death, I am writing this project. I believe in the feasibility of my idea, and this belief supports me in my terrible position ... I will calmly face death, knowing that my idea will not die with me.
The idea of ​​using rockets for space flights was proposed at the beginning of our century by the Russian scientist Konstantin Eduardovich Tsiolkovsky. In 1903, an article by a teacher of the Kaluga gymnasium K.E. Tsiolkovsky "Research of world spaces by jet devices". This work contained the most important mathematical equation for astronautics, now known as the “Tsiolkovsky formula”, which described the motion of a body of variable mass. Subsequently, he developed a scheme for a liquid-fuel rocket engine, proposed a multi-stage rocket design, and expressed the idea of ​​the possibility of creating entire space cities in near-Earth orbit. He showed that the only apparatus capable of overcoming gravity is a rocket, i.e. an apparatus with a jet engine using fuel and an oxidizer located on the apparatus itself. Soviet rockets were the first to reach the Moon, circled the Moon and photographed its invisible side from the Earth, were the first to reach the planet Venus and delivered scientific instruments to its surface. In 1986, two Soviet spacecraft "Vega-1" and "Vega-2" studied Halley's Comet at close range, approaching the Sun once every 76 years.

Jet propulsion "Intercontinental missile"
Mankind has always dreamed of traveling into space. A variety of means to achieve this goal were offered by writers - science fiction, scientists, dreamers. But for many centuries, not a single scientist, not a single science fiction writer could invent the only means at the disposal of man, with the help of which it is possible to overcome the force of gravity and fly into space. K. E. Tsiolkovsky is the founder of the theory of space flights.
For the first time, the dream and aspirations of many people for the first time could be brought closer to reality by the Russian scientist Konstantin Eduardovich Tsiolkovsky (1857-1935), who showed that the only device capable of overcoming gravity is a rocket, he first presented scientific proof of the possibility of using a rocket to fly into outer space , beyond the earth's atmosphere and to other planets of the solar system. Tsoilkovsky called a rocket an apparatus with a jet engine that uses the fuel and oxidizer on it.
As you know from the course of physics, a shot from a gun is accompanied by recoil. According to Newton's laws, a bullet and a gun would scatter in different directions with the same speed if they had the same mass. The discarded mass of gases creates a reactive force, due to which movement can be ensured both in air and in airless space, this is how recoil occurs. The greater the recoil force our shoulder feels, the greater the mass and speed of the outflowing gases, and, consequently, the stronger the reaction of the gun, the greater the reactive force. These phenomena are explained by the law of conservation of momentum:
the vector (geometric) sum of the impulses of the bodies that make up a closed system remains constant for any movements and interactions of the bodies of the system.
The presented formula of Tsiolkovsky is the foundation on which the entire calculation of modern missiles is based. The Tsiolkovsky number is the ratio of the mass of fuel to the mass of the rocket at the end of engine operation - to the weight of an empty rocket.
Thus, it was found that the maximum achievable speed of the rocket depends primarily on the speed of the outflow of gases from the nozzle. And the speed of the exhaust gases of the nozzle, in turn, depends on the type of fuel and the temperature of the gas jet. So the higher the temperature, the faster the speed. Then for a real rocket you need to choose the most high-calorie fuel that gives the greatest amount of heat. The formula shows that, among other things, the speed of a rocket depends on the initial and final mass of the rocket, on what part of its weight falls on fuel, and what part - on useless (in terms of flight speed) structures: body, mechanisms, etc. d.
The main conclusion from this formula of Tsiolkovsky for determining the speed of a space rocket is that in airless space the rocket will develop the greater the speed, the greater the speed of the outflow of gases and the greater the number of Tsiolkovsky.

"Physical foundations of the jet engine"
At the heart of modern powerful jet engines of various types is the principle of direct reaction, i.e. the principle of creating a driving force (or thrust) in the form of a reaction (recoil) of a jet of "working substance" flowing out of the engine, usually hot gases. In all engines, there are two processes of energy conversion. First, the chemical energy of the fuel is converted into thermal energy of the combustion products, and then the thermal energy is used to perform mechanical work. Such engines include reciprocating engines of automobiles, diesel locomotives, steam and gas turbines of power plants, etc. After hot gases have formed in the heat engine, containing large thermal energy, this energy must be converted into mechanical energy. After all, engines serve to make mechanical work, to “move” something, to put it into action, it doesn’t matter whether it is a dynamo, please add drawings of a power plant, a diesel locomotive, a car or an airplane. In order for the thermal energy of gases to be converted into mechanical energy, their volume must increase. With such an expansion, the gases do the work for which their internal and thermal energy is expended.
The jet nozzle can have various shapes, and, moreover, a different design, depending on the type of engine. The main thing is the speed with which the gases flow out of the engine. If this outflow velocity does not exceed the speed with which sound waves propagate in the outflowing gases, then the nozzle is a simple cylindrical or narrowing pipe section. If the outflow velocity must exceed the speed of sound, then the nozzle is given the shape of an expanding pipe or, first, narrowing, and then expanding (Love's nozzle). Only in a tube of such a shape, as theory and experience show, is it possible to disperse the gas to supersonic speeds, to step over the "sonic barrier".

"Classification of jet engines and features of their use"
However, this mighty trunk, the principle of direct reaction, gave life to a huge crown of the "family tree" of the family of jet engines. To get acquainted with the main branches of its crown, crowning the "trunk" of the direct reaction. Soon, as can be seen from the figure (see below), this trunk is divided into two parts, as if split by a lightning strike. Both new trunks are equally decorated with mighty crowns. This division occurred due to the fact that all "chemical" jet engines are divided into two classes, depending on whether they use ambient air for their work or not.
In a compressorless engine of another type, a ramjet, there is not even this valve grid and the pressure in the combustion chamber rises as a result of dynamic pressure, i.e. deceleration of the oncoming air flow entering the engine in flight. It is clear that such an engine is able to work only when the aircraft is already flying at a sufficiently high speed, it will not develop thrust in the parking lot. But on the other hand, at a very high speed, 4-5 times the speed of sound, a ramjet develops very high thrust and consumes less fuel than any other "chemical" jet engine under these conditions. That's why ramjet motors.
etc.................

For many people, the very concept of “jet propulsion” is strongly associated with modern achievements in science and technology, especially physics, and images of jet aircraft or even spacecraft flying at supersonic speeds with the help of the notorious jet engines appear in their heads. In fact, the phenomenon of jet propulsion is much more ancient than even man himself, because it appeared long before us, people. Yes, jet propulsion is actively represented in nature: jellyfish, cuttlefish have been swimming in the depths of the sea for millions of years according to the same principle that modern supersonic jet aircraft fly today.

History of jet propulsion

Since ancient times, various scientists have observed the phenomena of jet propulsion in nature, as the ancient Greek mathematician and mechanic Heron wrote about it before anyone else, however, he never went beyond theory.

If we talk about the practical application of jet propulsion, then the inventive Chinese were the first here. Around the 13th century, they guessed to borrow the principle of movement of octopuses and cuttlefish in the invention of the first rockets, which they began to use both for fireworks and for military operations (as military and signal weapons). A little later, this useful invention of the Chinese was adopted by the Arabs, and from them the Europeans.

Of course, the first conditionally jet rockets had a relatively primitive design and for several centuries they practically did not develop in any way, it seemed that the history of the development of jet propulsion froze. A breakthrough in this matter occurred only in the 19th century.

Who discovered jet propulsion?

Perhaps, the laurels of the pioneer of jet propulsion in the "new time" can be awarded to Nikolai Kibalchich, not only a talented Russian inventor, but also a part-time revolutionary-People's Volunteer. He created his project of a jet engine and an aircraft for people while sitting in a royal prison. Later, Kibalchich was executed for his revolutionary activities, and his project remained gathering dust on the shelves in the archives of the tsarist secret police.

Later, the works of Kibalchich in this direction were discovered and supplemented by the works of another talented scientist, K. E. Tsiolkovsky. From 1903 to 1914, he published a series of papers that convincingly proved the possibility of using jet propulsion in the creation of spacecraft for space exploration. He also formed the principle of using multi-stage rockets. To this day, many of Tsiolkovsky's ideas are used in rocket science.

Examples of jet propulsion in nature

Surely, while swimming in the sea, you saw jellyfish, but you hardly thought that these amazing (and also slow) creatures move just the same thanks to jet propulsion. Namely, by reducing their transparent dome, they squeeze out water, which serves as a kind of “jet engine” for jellyfish.

The cuttlefish also has a similar mechanism of movement - through a special funnel in front of the body and through the side slit, it draws water into its gill cavity, and then vigorously throws it out through the funnel, directed back or to the side (depending on the direction of movement needed by the cuttlefish).

But the most interesting jet engine created by nature is found in squids, which can rightly be called "live torpedoes". After all, even the body of these animals in its form resembles a rocket, although in truth everything is exactly the opposite - this rocket copies the body of a squid with its design.

If the squid needs to make a quick throw, it uses its natural jet engine. Its body is surrounded by a mantle, a special muscle tissue, and half of the volume of the entire squid falls on the mantle cavity, into which it sucks water. Then he abruptly throws out the collected stream of water through a narrow nozzle, while folding all his ten tentacles over his head in such a way as to acquire a streamlined shape. Thanks to such perfect jet navigation, squids can reach an impressive speed of 60-70 km per hour.

Among the owners of a jet engine in nature there are also plants, namely the so-called "mad cucumber". When its fruits ripen, in response to the slightest touch, it shoots gluten with seeds

Law of jet propulsion

Squids, “mad cucumbers”, jellyfish and other cuttlefish have been using jet propulsion since ancient times, without thinking about its physical essence, but we will try to figure out what the essence of jet propulsion is, what motion is called jet, to give it a definition.

To begin with, you can resort to a simple experiment - if you inflate an ordinary balloon with air and, without tying it, let it fly, it will fly rapidly until it runs out of air. This phenomenon explains Newton's third law, which says that two bodies interact with forces equal in magnitude and opposite in direction.

That is, the force of the impact of the ball on the air flows escaping from it is equal to the force with which the air repels the ball from itself. A rocket also works on a principle similar to a ball, which ejects part of its mass at great speed, while receiving strong acceleration in the opposite direction.

Law of conservation of momentum and jet propulsion

Physics explains the process of jet propulsion. Momentum is the product of a body's mass and its velocity (mv). When a rocket is at rest, its momentum and velocity are zero. When a jet begins to be ejected from it, then the rest, according to the law of conservation of momentum, must acquire such a speed at which the total momentum will still be equal to zero.

Jet propulsion formula

In general, jet propulsion can be described by the following formula:
m s v s +m p v p =0
m s v s =-m p v p

where m s v s is the momentum generated by the jet of gases, m p v p is the momentum received by the rocket.

The minus sign shows that the direction of the rocket and the force of the jet propulsion are opposite.

Jet propulsion in technology - the principle of operation of a jet engine

V modern technology jet propulsion plays a very important role, as jet engines propel aircraft and spacecraft. The jet engine device itself may differ depending on its size and purpose. But one way or another, each of them has

• fuel supply,
• chamber, for combustion of fuel,
• nozzle, the task of which is to accelerate the jet stream.

This is what a jet engine looks like.

The use of jet propulsion in nature Many of us in our lives have met while swimming in the sea with jellyfish. But few people thought that jellyfish also use jet propulsion to move around. And often the efficiency of marine invertebrates when using jet propulsion is much higher than that of techno inventions.

Cuttlefish Cuttlefish, like most cephalopods, moves in the water in the following way. She takes water into the gill cavity through a lateral slit and a special funnel in front of the body, and then vigorously throws a stream of water through the funnel. The cuttlefish directs the funnel tube to the side or back and, rapidly squeezing water out of it, can move in different directions.

Squid The squid is the largest invertebrate inhabitant of the ocean depths. It moves according to the principle of jet propulsion, absorbing water into itself, and then pushing it with great force through a special hole - a "funnel", and at high speed (about 70 km / h) moves back in jolts. In this case, all ten tentacles of the squid are collected in a knot above the head and it acquires a streamlined shape.

Flying squid This is a small animal about the size of a herring. He pursues fish with such swiftness that he often jumps out of the water, rushing over its surface like an arrow. Having developed maximum jet thrust in the water, the pilot squid takes off into the air and flies over the waves for more than fifty meters. The apogee of the flight of a living rocket lies so high above the water that flying squids often fall on the decks of ocean-going ships. Four or five meters is not a record height to which squids rise into the sky. Sometimes they fly even higher.

Octopus Octopuses can also fly. The French naturalist Jean Verany saw an ordinary octopus speed up in an aquarium and suddenly jump out of the water backwards. Describing in the air an arc about five meters long, he plopped back into the aquarium. Gaining speed for the jump, the octopus moved not only due to jet thrust, but also rowed with tentacles.

Mad Cucumber In the southern countries (and here on the Black Sea coast too) a plant called "mad cucumber" grows. One has only to lightly touch the ripe fruit, similar to a cucumber, as it bounces off the stalk, and liquid with seeds flies out of the fruit at a speed of up to 10 m / s through the hole formed. Shoots a mad cucumber (otherwise it is called a "lady's pistol") more than 12 m.