In this section we will consider the movement of bodies of variable mass. This type of movement is often found in nature and in technical systems. As examples, we can mention:
Fall of an evaporating drop;
The movement of a melting iceberg on the surface of the ocean;
Movement of a squid or jellyfish;
Rocket flight.
Differential equation of jet propulsion
Jet propulsion is based on Newton's third law , according to which “the action force is equal in magnitude and opposite in direction to the reaction force.” Hot gases escaping from the rocket nozzle create an action force. A reaction force acting in the opposite direction is called traction force. This force is what ensures the acceleration of the rocket.
Let the initial mass of the rocket be \(m,\) and its initial speed be \(v.\) After some time \(dt\), the mass of the rocket will decrease by the amount \(dm\) as a result of fuel combustion. This will increase the rocket speed by \(dv.\) Apply law of conservation of momentum to the "rocket + gas flow" system. At the initial moment of time, the momentum of the system is \(mv.\) After a short time \(dt\), the momentum of the rocket will be \[(p_1) = \left((m - dm) \right)\left((v + dv) \right),\] and the momentum associated with the exhaust gases in the coordinate system relative to the Earth will be equal to \[(p_2) = dm\left((v - u) \right),\] where \(u\) − gas flow rate relative to the Earth. Here we took into account that the speed of gas outflow is directed in the direction opposite to the speed of the rocket (Figure \(1\)). Therefore, there is a minus sign in front of \(u\).
In accordance with the law of conservation of total momentum of the system, we can write: \[ (p = (p_1) + (p_2),)\;\; (\Rightarrow mv = \left((m - dm) \right)\left((v + dv) \right) + dm\left((v - u) \right).) \]
Fig.1 |
Transforming this equation, we get: \[\require(cancel) \cancel(\color(blue)(mv)) = \cancel(\color(blue)(mv)) - \cancel(\color(red)(vdm) ) + mdv - dmdv + \cancel(\color(red)(vdm)) - udm. \] In the last equation, the term \(dmdv,\) can be neglected when considering small changes in these quantities. As a result, the equation will be written in the form \ Divide both sides by \(dt,\) to transform the equation into the form Newton's second law :\ This equation is called differential equation of jet motion . The right side of the equation is traction force\(T:\) \ From the resulting formula it is clear that the traction force is proportional gas flow rates And fuel combustion rate . Of course, this differential equation describes the ideal case. It doesn't take into account gravity And aerodynamic force . Taking them into account leads to a significant complication of the differential equation.
Tsiolkovsky formula
If we integrate the differential equation derived above, we obtain the dependence of the rocket speed on the mass of the burned fuel. The resulting formula is called ideal jet propulsion equation or Tsiolkovsky formula , who brought it out in \(1897\) year.
To obtain the indicated formula, it is convenient to rewrite the differential equation in the following form: \ Separating the variables and integrating, we find: \[ (dv = u\frac((dm))(m),)\;\; (\Rightarrow \int\limits_((v_0))^((v_1)) (dv) = \int\limits_((m_0))^((m_1)) (u\frac((dm))(m)) .) \] Note that \(dm\) denotes a decrease in mass. Therefore, we take the increment \(dm\) with a negative sign. As a result, the equation takes the form: \[ (\left. v \right|_((v_0))^((v_1)) = - u\left. (\left((\ln m) \right)) \right |_((m_0))^((m_1)),)\;\; (\Rightarrow (v_1) - (v_0) = u\ln \frac(((m_0)))(((m_1))).) \] where \((v_0)\) and \((v_1)\) are the initial and final speed of the rocket, and \((m_0)\) and \((m_1)\) are the initial and final mass of the rocket, respectively.
Assuming \((v_0) = 0,\) we obtain the formula derived by Tsiolkovsky: \ This formula determines the speed of the rocket depending on the change in its mass as the fuel burns. Using this formula, you can roughly estimate the amount of fuel required to accelerate a rocket to a certain speed.
Newton's laws help explain a very important mechanical phenomenon - jet propulsion. This is the name given to the movement of a body that occurs when some part of it is separated from it at any speed.
Let's take, for example, a children's rubber ball, inflate it and release it. We will see that when the air begins to leave it in one direction, the ball itself will fly in the other. This is reactive movement.
Some representatives of the animal world move according to the principle of jet propulsion, such as squids and octopuses. Periodically throwing out the water they absorb, they are able to reach speeds of up to 60-70 km/h. Jellyfish, cuttlefish and some other animals move in a similar way.
Examples of jet propulsion can also be found in the plant world. For example, the ripened fruits of a “mad” cucumber, with the slightest touch, bounce off the stalk and a bitter liquid with seeds is forcefully thrown out of the hole formed at the site of the separated stalk; the cucumbers themselves fly off in the opposite direction.
The reactive motion that occurs when water is released can be observed in the following experiment. Pour water into a glass funnel connected to a rubber tube with an L-shaped tip (Fig. 20). We will see that when water begins to flow out of the tube, the tube itself will begin to move and deviate in the direction opposite to the direction of flow of water.
Flights are based on the principle of jet propulsion missiles. A modern space rocket is a very complex aircraft consisting of hundreds of thousands and millions of parts. The mass of the rocket is enormous. It consists of the mass of the working fluid (i.e., hot gases formed as a result of fuel combustion and emitted in the form of a jet stream) and the final or, as they say, “dry” mass of the rocket remaining after the working fluid is ejected from the rocket.
The “dry” mass of the rocket, in turn, consists of the mass of the structure (i.e. the rocket shell, its engines and control system) and the mass of the payload (i.e. scientific equipment, the body of the spacecraft launched into orbit, the crew and the system ship life support).
As the working fluid expires, the released tanks, excess parts of the shell, etc. begin to burden the rocket with unnecessary cargo, making it difficult to accelerate. Therefore, to achieve cosmic speeds, composite (or multi-stage) rockets are used (Fig. 21). At first, only the first stage 1 blocks work in such rockets. When the fuel reserves in them run out, they are separated and the second stage 2 is turned on; after the fuel in it is exhausted, it is also separated and the third stage 3 is turned on. The satellite or any other spacecraft located in the head of the rocket is covered with a head fairing 4, the streamlined shape of which helps to reduce air resistance when the rocket flies in the Earth's atmosphere.
When a jet of gas is ejected from a rocket at high speed, the rocket itself rushes in the opposite direction. Why is this happening?
According to Newton's third law, the force F with which the rocket acts on the working fluid is equal in magnitude and opposite in direction to the force F" with which the working fluid acts on the rocket body:
Force F" (which is called reactive force) accelerates the rocket.
From equality (10.1) it follows that the impulse imparted to the body is equal to the product of the force and the time of its action. Therefore, equal forces acting for the same time impart equal impulses to bodies. In this case, the pulse m p v p acquired by the rocket must correspond to the pulse m gas v gas of the ejected gases:
m р v р = m gas v gas
It follows that the speed of the rocket 
Let's analyze the resulting expression. We see that the speed of the rocket is greater, the greater the speed of the emitted gases and the greater the ratio of the mass of the working fluid (i.e., the mass of the fuel) to the final (“dry”) mass of the rocket.
Formula (12.2) is approximate. It does not take into account that as the fuel burns, the mass of the flying rocket becomes less and less. The exact formula for rocket speed was first obtained in 1897 by K. E. Tsiolkovsky and therefore bears his name.
The Tsiolkovsky formula allows you to calculate the fuel reserves required to impart a given rocket speed. Table 3 shows the ratio of the initial mass of the rocket m0 to its final mass m, corresponding to different velocities of the rocket at a gas jet speed (relative to the rocket) v = 4 km/s. 
For example, to impart to a rocket a speed exceeding the speed of gas flow by 4 times (v p = 16 km/s), it is necessary that the initial mass of the rocket (including fuel) exceed the final (“dry”) mass of the rocket by 55 times (m 0 /m = 55). This means that the lion's share of the total mass of the rocket at launch should be the mass of fuel. The payload, in comparison, should have a very small mass.
An important contribution to the development of the theory of jet propulsion was made by a contemporary of K. E. Tsiolkovsky, the Russian scientist I. V. Meshchersky (1859-1935). The equation of motion of a body with variable mass is named after him.
1. What is jet propulsion? Give examples. 2. In the experiment shown in Figure 22, when water flows out through curved tubes, the bucket rotates in the direction indicated by the arrow. Explain the phenomenon. 3. What determines the speed acquired by a rocket after fuel combustion?
Ministry of Education and Science of the Russian Federation
FGOU SPO "Perevozsky Construction College"
Essay
discipline:
Physics
subject: Jet propulsion
Completed:
Student
Groups 1-121
Okuneva Alena
Checked:
P.L.Vineaminovna
Perevoz city
2011
Content:
- Introduction: What is Jet Propulsion………………………………………………………… …..…………………………………..3
Law of conservation of momentum……………………………………………………………….4
Application of jet propulsion in nature…………………………..….…....5
Application of jet propulsion in technology…….…………………...…..….….6
Jet propulsion “Intercontinental missile”…………..………...…7
Physical basis of jet engine operation..................... .................... 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 references……………………………………………………… …..12
"Jet propulsion"
Reactive motion is the movement of a body caused by the separation of some part of it from it at a certain speed. Jet motion is described based on the law of conservation of momentum.
Jet propulsion, now used in airplanes, rockets and spacecraft, is characteristic of octopuses, squids, cuttlefish, jellyfish - all of them, without exception, use the reaction (recoil) of an ejected stream of water for swimming.
Examples of jet propulsion can also be found in the plant world.
In southern countries there grows a plant called "mad cucumber". As soon as you lightly touch a ripe fruit, similar to a cucumber, it bounces off the stalk, and through the resulting hole, liquid with seeds flies out of the fruit like a fountain at a speed of up to 10 m/s.
The cucumbers themselves fly off in the opposite direction. The mad cucumber (otherwise called the “ladies’ pistol”) shoots at 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. Let us consider two interacting bodies that are part of a closed system.
We denote the forces of interaction between these bodies by and According to Newton’s third law If these bodies interact during time t, then the impulses of the interaction forces are equal in magnitude and directed in opposite directions: Let us apply Newton’s second law to these bodies:
This equality means that as a result of the interaction of two bodies, their total momentum has not changed. Considering now all possible pair interactions of bodies included in a closed system, we can conclude that the internal forces of a closed system cannot change its total momentum, that is, the vector sum of the momentum of all bodies included in this system. A significant reduction in rocket launch mass can be achieved by usingmultistage rockets, when the rocket stages separate as the fuel burns out. The masses of containers that contained fuel, spent engines, control systems, etc. are excluded from the process of subsequent rocket acceleration. It is along the path of creating economical multi-stage rockets that modern rocket science is developing.
"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 stream of water thrown out of the shell during a sharp compression of its valves.
Octopus
Cuttlefish, like most cephalopods, moves in water in the following way. She takes water into the gill cavity through a side slit and a special funnel in front of the body, and then energetically throws out a stream of water through the funnel. The cuttlefish directs the funnel tube to the side or back and, quickly squeezing water out of it, can move in different directions.
The 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 of which the 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 salp contract, the whole body contracts, and water is pushed out through the posterior opening. The reaction of the escaping jet pushes the salpa forward. The squid's jet engine is of greatest interest. The squid is the largest invertebrate inhabitant of the ocean depths. Squids have achieved the highest perfection in jet navigation. Even their body, with its external shape, copies a rocket. 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 several heavy stones, then throwing stones in a certain direction will move you in the opposite direction. The same will happen in outer space, but there they use jet engines for this.
"Application of jet propulsion in technology"
At the end of the first millennium AD, China invented jet propulsion, which powered rockets - bamboo tubes filled with gunpowder, they were also used as fun. One of the first car projects was also with a jet engine and this project belonged to Newton.
The author of the world's first project of a jet aircraft intended for human flight was the Russian revolutionary N.I. Kibalchich. He was executed on April 3, 1881 for his participation in the assassination attempt on Emperor Alexander II. He developed his project in prison after being sentenced to death. 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 faith supports me in my terrible situation... 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 this century by the Russian scientist Konstantin Eduardovich Tsiolkovsky. In 1903, an article by Kaluga gymnasium teacher K.E. appeared in print. Tsiolkovsky “Exploration of world spaces using reactive instruments.” 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 design 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 low-Earth orbit. He showed that the only device capable of overcoming gravity is a rocket, i.e. a device with a jet engine that uses fuel and oxidizer located on the device itself. Soviet rockets were the first to reach the Moon, circled the Moon and photographed its side invisible from Earth, and were the first to reach the planet Venus and deliver scientific instruments to its surface. In 1986, two Soviet spacecraft, Vega 1 and Vega 2, closely examined Halley's Comet, which approaches the Sun once every 76 years.
Jet propulsion "Intercontinental missile"
Humanity has always dreamed of traveling into space. Writers - science fiction writers, scientists, dreamers - proposed a variety of means to achieve this goal. But for many centuries, not a single scientist or science fiction writer has been able to invent the only means at a person’s disposal with which one can overcome the force of gravity and fly into space. K. E. Tsiolkovsky is the founder of the theory of space flight.
For the first time, the dream and aspirations of many people were 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 for the first time presented scientific evidence of the possibility of using a rocket for flights into outer space , beyond the Earth's atmosphere and to other planets of the solar system. Tsoilkovsky called a rocket a device with a jet engine that uses the fuel and oxidizer on it.
As you know from a physics course, a shot from a gun is accompanied by recoil. According to Newton's laws, a bullet and a gun would fly in different directions at the same speed if they had the same mass. The ejected mass of gases creates a reactive force, thanks to which movement can be ensured, both in air and in airless space, and thus recoil occurs. The greater the recoil force our shoulder feels, the greater the mass and speed of the escaping gases, and, therefore, 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 Tsiolkovsky formula is the foundation on which the entire calculation of modern missiles is based. The Tsiolkovsky number is the ratio of the fuel mass to the mass of the rocket at the end of engine operation - to the weight of the empty rocket.
Thus, we found that the maximum achievable speed of the rocket depends primarily on the speed of gas flow from the nozzle. And the flow rate of the nozzle gases, in turn, depends on the type of fuel and the temperature of the gas jet. This means that the higher the temperature, the greater the speed. Then for a real rocket you need to select the most high-calorie fuel that produces the greatest amount of heat. The formula shows that, among other things, the speed of the rocket depends on the initial and final mass of the rocket, on what part of its weight is fuel, and what part is on useless (from the point of view of flight speed) structures: body, mechanisms, etc. d.
The main conclusion from this Tsiolkovsky formula 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 gas outflow and the greater the Tsiolkovsky number.
"Physical basis of jet engine operation"
Modern powerful jet engines of various types are based on 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 stream of “working substance” flowing from the engine, usually hot gases. In all engines there are two energy conversion processes. First, the chemical energy of the fuel is converted into thermal energy of combustion products, and then the thermal energy is used to perform mechanical work. Such engines include piston engines of cars, diesel locomotives, steam and gas turbines of power plants, etc. After hot gases containing large thermal energy have been generated in a heat engine, this energy must be converted into mechanical energy. After all, engines serve to perform mechanical work, to “move” something, to put it into action, no matter whether it is a dynamo, if asked to be supplemented with drawings of a power plant, a diesel locomotive, a car or an airplane. In order for the thermal energy of gases to transform into mechanical energy, their volume must increase. With such expansion, gases perform work, which consumes their internal and thermal energy.
The jet nozzle can have different shapes, and, moreover, different designs depending on the type of engine. The main thing is the speed at which 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 tapered section of pipe. If the outflow speed should exceed the speed of sound, then the nozzle is shaped like an expanding pipe or first narrowing and then expanding (Lavl nozzle). Only in a pipe of this shape, as theory and experience show, can gas be accelerated to supersonic speeds and crossed the “sound barrier.”
“Classification of jet engines and features of their use”
However, this mighty trunk, the principle of direct reaction, gave birth to a huge crown of the "family tree" of the jet engine family. To get acquainted with the main branches of its crown, crowning the “trunk” of direct reaction. Soon, as you can see from the picture (see below), this trunk is divided into two parts, as if split by a lightning strike. Both new trunks are equally decorated with powerful crowns. This division occurred because all “chemical” jet engines are divided into two classes depending on whether they use ambient air for their operation or not.
In a non-compressor engine of another type, direct-flow, there is not even this valve grid and the pressure in the combustion chamber increases as a result of the high-speed pressure, i.e. braking the oncoming air flow entering the engine in flight. It is clear that such an engine is capable of operating only when the aircraft is already flying at a sufficiently high speed; it will not develop thrust when parked. But at a very high speed, 4-5 times the speed of sound, a ramjet engine develops very high thrust and consumes less fuel than any other “chemical” jet engine under these conditions. That's why ramjet engines.
etc.................
Jet propulsion in nature and technology
ABSTRACT ON PHYSICS
Jet propulsion- movement that occurs when any part of it is separated from the body at a certain speed.
Reactive force occurs without any interaction with external bodies.
Application of jet propulsion in nature
Many of us in our lives have encountered jellyfish while swimming in the sea. In any case, there are quite enough of them in the Black Sea. But few people thought that jellyfish also use jet propulsion to move. In addition, this is how dragonfly larvae and some species of marine plankton move. And often the efficiency of marine invertebrate animals when using jet propulsion is much higher than that of technological inventions.
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 stream of water thrown out of the shell during a sharp compression of its valves.
Octopus
Cuttlefish
Cuttlefish, like most cephalopods, moves in water in the following way. She takes water into the gill cavity through a side slit and a special funnel in front of the body, and then energetically throws out a stream of water through the funnel. The cuttlefish directs the funnel tube to the side or back and, quickly squeezing water out of it, can move in different directions.
The 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 of which the 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 salp contract, the whole body contracts, and water is pushed out through the posterior opening. The reaction of the escaping jet pushes the salpa forward.
The squid's jet engine is of greatest interest. The squid is the largest invertebrate inhabitant of the ocean depths. Squids have achieved the highest perfection in jet navigation. Even their body, with its external forms, copies the rocket (or better said, the rocket copies the squid, since it has indisputable priority in this matter). When moving slowly, the squid uses a large diamond-shaped fin that periodically bends. It uses a jet engine to throw quickly. Muscle tissue - the mantle surrounds the mollusk's body on all sides; the volume of its cavity is almost half the volume of the squid's body. The animal sucks water inside the mantle cavity, and then sharply throws out a stream of water through a narrow nozzle and moves backwards with high speed pushes. At the same time, all ten tentacles of the squid are gathered into a knot above its head, and it takes on a streamlined shape. The nozzle is equipped with a special valve, and the muscles can rotate it, changing the direction of movement. The squid engine is very economical, it is capable of reaching speeds of up to 60 - 70 km/h. (Some researchers believe that even up to 150 km/h!) No wonder the squid is called a “living torpedo.” By bending the bundled tentacles to the right, left, up or down, the squid turns in one direction or another. Since such a steering wheel is very large compared to the animal itself, its slight movement is enough for the squid, even at full speed, to easily dodge a collision with an obstacle. A sharp turn of the steering wheel - and the swimmer rushes in the opposite direction. So he bent the end of the funnel back and now slides head first. He bent it to the right - and the jet push threw him to the left. But when you need to swim quickly, the funnel always sticks out right between the tentacles, and the squid rushes tail first, just as a crayfish would run - a fast walker endowed with the agility of a racer.
If there is no need to rush, squids and cuttlefish swim with undulating fins - miniature waves run over them from front to back, and the animal glides gracefully, occasionally pushing itself also with a stream of water thrown out from under the mantle. Then the individual shocks that the mollusk receives at the moment of eruption of water jets are clearly visible. Some cephalopods can reach speeds of up to fifty-five kilometers per hour. It seems that no one has made direct measurements, but this can be judged by the speed and flight range of flying squids. And it turns out that octopuses have such talents in their family! The best pilot among mollusks is the squid Stenoteuthis. English sailors call it flying squid (“flying squid”). This is a small animal about the size of a herring. It chases fish with such speed that it often jumps out of the water, skimming over its surface like an arrow. He resorts to this trick to save his life from predators - tuna and mackerel. 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 a living rocket's flight lies so high above the water that flying squids often end up on the decks of ocean-going ships. Four to five meters is not a record height to which squids rise into the sky. Sometimes they fly even higher.
The English mollusk researcher Dr. Rees described in a scientific article a squid (only 16 centimeters long), which, having flown a fair distance through the air, fell on the bridge of a yacht, which rose almost seven meters above the water.
It happens that a lot of flying squids fall on the ship in a sparkling cascade. The ancient writer Trebius Niger once told a sad story about a ship that allegedly sank under the weight of flying squids that fell on its deck. Squids can take off without acceleration.
Octopuses can also fly. French naturalist Jean Verani saw how an ordinary octopus accelerated in an aquarium and suddenly jumped out of the water backwards. Having described an arc about five meters long in the air, he plopped back into the aquarium. When picking up speed to jump, the octopus moved not only due to jet thrust, but also rowed with its tentacles.
Baggy octopuses swim, of course, worse than squids, but at critical moments they can show a record class for the best sprinters. California Aquarium staff tried to photograph an octopus attacking a crab. The octopus rushed at its prey with such speed that the film, even when filming at the highest speeds, always contained grease. This means that the throw lasted hundredths of a second! Typically, octopuses swim relatively slowly. Joseph Seinl, who studied the migrations of octopuses, calculated: an octopus half a meter in size swims through the sea at an average speed of about fifteen kilometers per hour. Each jet of water thrown out of the funnel pushes it forward (or rather, backward, since the octopus swims backwards) two to two and a half meters.
Jet motion can also be found in the plant world. For example, the ripened fruits of the “mad cucumber”, with the slightest touch, bounce off the stalk, and a sticky liquid with seeds is forcefully thrown out of the resulting hole. The cucumber itself flies off in the opposite direction up to 12 m.
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 several heavy stones, then throwing stones in a certain direction will move you in the opposite direction. The same will happen in outer space, but there they use jet engines for this.
Everyone knows that a shot from a gun is accompanied by recoil. If the weight of the bullet were equal to the weight of the gun, they would fly apart at the same speed. Recoil occurs because the ejected mass of gases creates a reactive force, thanks to which movement can be ensured both in air and in airless space. And the greater the mass and speed of the flowing gases, the greater the recoil force our shoulder feels, the stronger the reaction of the gun, the greater the reactive force.
Application of jet propulsion in technology
For many centuries, humanity has dreamed of space flight. Science fiction writers have proposed a variety of means to achieve this goal. In the 17th century, a story by the French writer Cyrano de Bergerac about a flight to the moon appeared. The hero of this story reached the Moon in an iron cart, over which he constantly threw a strong magnet. Attracted to him, the cart rose higher and higher above the Earth until it reached the Moon. And Baron Munchausen said that he climbed to the moon along a bean stalk.
At the end of the first millennium AD, China invented jet propulsion, which powered rockets - bamboo tubes filled with gunpowder, they were also used as fun. One of the first car projects was also with a jet engine and this project belonged to Newton
The author of the world's first project of a jet aircraft intended for human flight was the Russian revolutionary N.I. Kibalchich. He was executed on April 3, 1881 for his participation in the assassination attempt on Emperor Alexander II. He developed his project in prison after being sentenced to death. 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 faith supports me in my terrible situation... 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 this century by the Russian scientist Konstantin Eduardovich Tsiolkovsky. In 1903, an article by Kaluga gymnasium teacher K.E. appeared in print. Tsiolkovsky “Exploration of world spaces using reactive instruments.” 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 design 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 low-Earth orbit. He showed that the only device capable of overcoming gravity is a rocket, i.e. a device with a jet engine that uses fuel and oxidizer located on the device itself.
Jet motion in nature and technology is a very common phenomenon. In nature, it occurs when one part of the body separates at a certain speed from some other part. In this case, the reactive force appears without the interaction of this organism with external bodies.
In order to understand what we are talking about, it is best to look at examples. in nature and technology are numerous. We will first talk about how animals use it, and then how it is used in technology.
Jellyfish, dragonfly larvae, plankton and mollusks
Many people, while swimming in the sea, came across jellyfish. In the Black Sea, in any case, there are plenty of them. However, not everyone realized that jellyfish move using jet propulsion. The same method is used by dragonfly larvae, as well as some representatives of marine plankton. The efficiency of invertebrate marine animals that use it is often much higher than that of technical inventions.
Many mollusks move in a way that interests us. Examples include cuttlefish, squid, and octopus. In particular, the scallop clam is able to move forward using a jet of water that is ejected from the shell when its valves are sharply compressed.
And these are just a few examples from the life of the animal world that can be cited to expand on the topic: “Jet propulsion in everyday life, nature and technology.”
How does a cuttlefish move?
The cuttlefish is also very interesting in this regard. Like many cephalopods, it moves in water using the following mechanism. Through a special funnel located in front of the body, as well as through a side slit, the cuttlefish takes water into its gill cavity. Then she vigorously throws it through the funnel. The cuttlefish directs the funnel tube back or to the side. The movement can be carried out in different directions.
The method that the salpa uses
The method that the salpa uses is also curious. This is the name of a sea animal that has a transparent body. When moving, the salpa draws in water using the front opening. The water ends up in a wide cavity, and gills are located diagonally inside it. The hole closes when the salpa takes a large sip of water. Its transverse and longitudinal muscles contract, compressing the entire body of the animal. Water is pushed out through the rear hole. The animal moves forward due to the reaction of the flowing jet.
Squids - "living torpedoes"
Perhaps the most interesting thing is the jet engine that the squid has. This animal is considered the largest representative of invertebrates, living at great ocean depths. In jet navigation, squids have achieved real perfection. Even the body of these animals resembles a rocket in its external shape. Or rather, this rocket copies the squid, since it is the squid that has the undisputed primacy in this matter. If it needs to move slowly, the animal uses a large diamond-shaped fin for this, which bends from time to time. If a quick throw is needed, a jet engine comes to the rescue.
The mollusk's body is surrounded on all sides by a mantle - muscle tissue. Almost half of the total volume of the animal’s body is the volume of its cavity. The squid uses the mantle cavity to move by sucking water inside it. Then he sharply throws out the collected stream of water through a narrow nozzle. As a result of this, it pushes backwards at high speed. At the same time, the squid folds all 10 tentacles into a knot above its head in order to acquire a streamlined shape. The nozzle contains a special valve, and the animal's muscles can turn it. Thus, the direction of movement changes.
Impressive squid speed
It must be said that the squid engine is very economical. The speed it is capable of reaching can reach 60-70 km/h. Some researchers even believe that it can reach up to 150 km/h. As you can see, the squid is not called the “living torpedo” for nothing. It can turn in the desired direction, bending its tentacles folded in a bundle down, up, left or right.
How does a squid control movement?
Since the steering wheel is very large compared to the size of the animal itself, only a slight movement of the steering wheel is sufficient for the squid to easily avoid a collision with an obstacle, even moving at maximum speed. If you turn it sharply, the animal will immediately rush in the opposite direction. The squid bends the end of the funnel back and, as a result, can slide head first. If he bends it to the right, he will be thrown to the left by the jet thrust. However, when it is necessary to swim quickly, the funnel is always located directly between the tentacles. In this case, the animal rushes tail first, like the running of a fast-moving crayfish if it had the agility of a racer.
When there is no need to rush, cuttlefish and squid swim, undulating with their fins. Miniature waves run across them from front to back. Squid and cuttlefish glide gracefully. They only push themselves from time to time with a stream of water that shoots out from under their mantle. The individual shocks that the mollusk receives during the eruption of jets of water are clearly visible at such moments.
Flying squid
Some cephalopods are capable of accelerating up to 55 km/h. It seems that no one has made direct measurements, but we can give such a figure based on the range and speed of flying squids. It turns out that there are such people. The Stenoteuthis squid is the best pilot of all mollusks. English sailors call it a flying squid (flying squid). This animal, the photo of which is presented above, is small in size, about the size of a herring. It chases fish so quickly that it often jumps out of the water, skimming like an arrow over its surface. He also uses this trick when he is in danger from predators - mackerel and tuna. Having developed maximum jet thrust in the water, the squid launches into the air and then flies more than 50 meters above the waves. When it flies, it is so high that frequent flying squids end up on the decks of ships. A height of 4-5 meters is by no means a record for them. Sometimes flying squids fly even higher.
Dr. Rees, a mollusk researcher from Great Britain, in his scientific article described a representative of these animals, whose body length was only 16 cm. However, he was able to fly a fair distance through the air, after which he landed on the bridge of a yacht. And the height of this bridge was almost 7 meters!
There are times when a ship is attacked by many flying squids at once. Trebius Niger, an ancient writer, once told a sad story about a ship that seemed unable to withstand the weight of these sea animals and sank. Interestingly, squids are able to take off even without acceleration.
Flying octopuses
Octopuses also have the ability to fly. Jean Verani, a French naturalist, watched one of them speed up in his aquarium and then suddenly jump out of the water. The animal described an arc of about 5 meters in the air and then plopped down into the aquarium. The octopus, gaining the speed necessary for the jump, moved not only thanks to jet thrust. It also paddled with its tentacles. Octopuses are baggy, so they swim worse than squids, but at critical moments these animals can give a head start to the best sprinters. California Aquarium workers wanted to take a photo of an octopus attacking a crab. However, the octopus, rushing at its prey, developed such a speed that the photographs, even when using a special mode, turned out to be blurred. This means that the throw lasted only a fraction of a second!
However, octopuses usually swim quite slowly. Scientist Joseph Seinl, who studied the migrations of octopuses, found that the octopus, whose size is 0.5 m, swims at an average speed of about 15 km/h. Each jet of water that it throws out of the funnel propels it forward (more precisely, backward, since it swims backwards) by about 2-2.5 m.
"Squirting cucumber"
Reactive movement in nature and technology can be considered using examples from the plant world to illustrate it. One of the most famous is the ripened fruits of the so-called They bounce off the stalk at the slightest touch. Then, from the resulting hole, a special sticky liquid containing the seeds is ejected with great force. The cucumber itself flies in the opposite direction at a distance of up to 12 m.
Law of conservation of momentum
You should definitely talk about it when considering jet motion in nature and technology. Knowledge of the law of conservation of momentum allows us to change, in particular, our own speed of movement if we are in open space. For example, you are sitting in a boat and you have several stones with you. If you throw them in a certain direction, the boat will move in the opposite direction. This law also applies in outer space. However, for this purpose they use
What other examples of jet propulsion can be noted in nature and technology? Very well illustrated with the example of a gun.
As you know, a shot from it is always accompanied by recoil. Let's say the weight of the bullet was equal to the weight of the gun. In this case, they would fly apart at the same speed. Recoil occurs because a reactive force is created, since there is a thrown mass. Thanks to this force, movement is ensured both in airless space and in the air. The greater the speed and mass of the flowing gases, the greater the recoil force that our shoulder feels. Accordingly, the stronger the reaction of the gun, the higher the reaction force.
Dreams of flying into space
Jet propulsion in nature and technology has been a source of new ideas for scientists for many years. For many centuries, humanity has dreamed of flying into space. The use of jet propulsion in nature and technology, it must be assumed, has by no means exhausted itself.
And it all started with a dream. Science fiction writers several centuries ago offered us various means of how to achieve this desired goal. In the 17th century, Cyrano de Bergerac, a French writer, created a story about a flight to the moon. His hero reached the Earth's satellite using an iron cart. He constantly threw a strong magnet over this structure. The cart, being attracted to him, rose higher and higher above the Earth. Eventually she reached the moon. Another famous character, Baron Munchausen, climbed to the moon using a bean stalk.
Of course, at that time little was known about how the use of jet propulsion in nature and technology could make life easier. But the flight of fancy certainly opened up new horizons.
On the way to an outstanding discovery
In China at the end of the 1st millennium AD. e. invented jet propulsion to power rockets. The latter were simply bamboo tubes that were filled with gunpowder. These rockets were launched for fun. The jet engine was used in one of the first automobile designs. This idea belonged to Newton.
N.I. also thought about how jet motion arises in nature and technology. Kibalchich. This is a Russian revolutionary, the author of the first project of a jet aircraft, which is intended for human flight. The revolutionary, unfortunately, was executed on April 3, 1881. Kibalchich was accused of participating in the assassination attempt on Alexander II. Already in prison, while awaiting execution of the death sentence, he continued to study such an interesting phenomenon as jet motion in nature and technology, which occurs when part of an object is separated. As a result of these researches, he developed his project. Kibalchich wrote that this idea supports him in his position. He is ready to calmly face his death, knowing that such an important discovery will not die with him.
Implementation of the idea of space flight
The manifestation of jet propulsion in nature and technology continued to be studied by K. E. Tsiolkovsky (his photo is presented above). At the beginning of the 20th century, this great Russian scientist proposed the idea of using rockets for space flights. His article on this issue appeared in 1903. It presented a mathematical equation that became the most important for astronautics. It is known in our time as the “Tsiolkovsky formula”. This equation described the motion of a body having variable mass. In his further works, he presented a diagram of a rocket engine running on liquid fuel. Tsiolkovsky, studying the use of jet propulsion in nature and technology, developed a multi-stage rocket design. He also came up with the idea of the possibility of creating entire space cities in low-Earth orbit. These are the discoveries the scientist came to while studying jet propulsion in nature and technology. Rockets, as Tsiolkovsky showed, are the only devices that can overcome a rocket. He defined it as a mechanism with a jet engine that uses the fuel and oxidizer located on it. This device transforms the chemical energy of the fuel, which becomes the kinetic energy of the gas jet. The rocket itself begins to move in the opposite direction.
Finally, scientists, having studied the reactive movement of bodies in nature and technology, moved on to practice. A large-scale task lay ahead to realize the long-standing dream of humanity. And a group of Soviet scientists, led by Academician S.P. Korolev, coped with it. She realized Tsiolkovsky's idea. The first artificial satellite of our planet was launched in the USSR on October 4, 1957. Naturally, a rocket was used.
Yu. A. Gagarin (pictured above) was the man who had the honor of being the first to fly in outer space. This important event for the world took place on April 12, 1961. Gagarin flew around the entire globe on the Vostok satellite. The USSR was the first state whose rockets reached the Moon, flew around it and photographed the side invisible from Earth. In addition, it was the Russians who visited Venus for the first time. They brought scientific instruments to the surface of this planet. American astronaut Neil Armstrong is the first person to walk on the surface of the Moon. He landed on it on July 20, 1969. In 1986, Vega 1 and Vega 2 (ships belonging to the USSR) explored at close range Halley's Comet, which approaches the Sun only once every 76 years. Space exploration continues...
As you can see, physics is a very important and useful science. Jet propulsion in nature and technology is just one of the interesting issues that are discussed in it. And the achievements of this science are very, very significant.
How jet propulsion is used in nature and technology these days
In physics, particularly important discoveries have been made in the last few centuries. While nature remains virtually unchanged, technology is developing at a rapid pace. Nowadays, the principle of jet propulsion is widely used not only by various animals and plants, but also in astronautics and aviation. In outer space there is no medium that a body could use to interact in order to change the magnitude and direction of its speed. That is why only rockets can be used to fly in airless space.
Today, jet propulsion is actively used in everyday life, nature and technology. It is no longer a mystery as it used to be. However, humanity should not stop there. New horizons are ahead. I would like to believe that the jet movement in nature and technology, briefly described in the article, will inspire someone to make new discoveries.