Examples of jet propulsion in the animal world. Biophysics: jet motion in living nature

The logic of nature is the most accessible and most useful logic for children.

Konstantin Dmitrievich Ushinsky(03.03.1823–03.01.1871) - Russian teacher, founder of scientific pedagogy in Russia.

BIOPHYSICS: JET MOTION IN LIVING NATURE

I invite readers of the green pages to look into fascinating world biophysicists and get to know the main principles of jet propulsion in wildlife. Today on the program: jellyfish cornermouth– the most large jellyfish Black Sea, scallops , enterprising rocker dragonfly larva, amazing the squid with its unrivaled jet engine and wonderful illustrations performed by a Soviet biologist and animal artist Kondakov Nikolai Nikolaevich.

A number of animals move in nature using the principle of jet propulsion, for example, jellyfish, scallops, dragonfly larvae, squid, octopus, cuttlefish... Let's get to know some of them better ;-)

The jet method of movement of jellyfish

Jellyfish are one of the most ancient and numerous predators on our planet! The body of a jellyfish is 98% water and is largely composed of watered connective tissue – mesoglea functioning like a skeleton. The basis of mesoglea is the protein collagen. The gelatinous and transparent body of the jellyfish is shaped like a bell or an umbrella (a few millimeters in diameter up to 2.5 m). Most jellyfish move in a reactive way, pushing water out of the umbrella cavity.

Jellyfish Cornerata(Rhizostomae), order of coelenterate animals of the scyphoid class. Jellyfish ( up to 65 cm in diameter) lacking marginal tentacles. The edges of the mouth are elongated into oral lobes with numerous folds that grow together to form many secondary oral openings. Touching the mouth blades may cause painful burns caused by the action of stinging cells. About 80 species; They live mainly in tropical, less often in temperate seas. In Russia - 2 types: Rhizostoma pulmo common in Black and Seas of Azov, Rhopilema asamushi found in the Sea of Japan.

Jet escape of sea clams scallops

Shellfish scallops, usually lying calmly on the bottom, when their main enemy approaches them - a delightfully slow, but extremely insidious predator - starfish- they sharply squeeze the doors of their sink, forcefully pushing water out of it. Thus using jet propulsion principle, they emerge and, continuing to open and close the shell, can swim a considerable distance. If for some reason the scallop does not have time to escape with its jet flight, starfish wraps her arms around it, opens the shell and eats it...

Sea Scallop(Pecten), a genus of marine invertebrate animals of the class of bivalve mollusks (Bivalvia). The scallop shell is rounded with a straight hinge edge. Its surface is covered with radial ribs diverging from the top. The shell valves are closed by one strong muscle. Pecten maximus, Flexopecten glaber live in the Black Sea; in the Seas of Japan and Okhotsk – Mizuhopecten yessoensis ( up to 17 cm in diameter).

Rocker dragonfly larva jet pump

Temperament Rocker dragonfly larvae, or eshny(Aeshna sp.) is no less predatory than its winged relatives. She lives for two and sometimes four years in the underwater kingdom, crawling along the rocky bottom, tracking down small aquatic inhabitants, happily including fairly large-sized tadpoles and fry in her diet. In moments of danger, the larva of the rocker dragonfly takes off and swims forward with jerks, driven by the work of the remarkable jet pump. Taking water into the hindgut and then abruptly throwing it out, the larva jumps forward, driven by the recoil force. Thus using jet propulsion principle, the larva of the rocker dragonfly with confident jerks and jerks hides from the threat pursuing it.

Reactive impulses of the nervous “freeway” of squids

In all the above cases (principles of jet propulsion of jellyfish, scallops, rocker dragonfly larvae), shocks and jerks are separated from each other by significant periods of time, therefore high speed of movement is not achieved. To increase the speed of movement, in other words, number of reactive impulses per unit time, is necessary increased nerve conduction which stimulate muscle contraction, servicing a living jet engine. Such large conductivity is possible with a large nerve diameter.

It is known that Squids have the largest nerve fibers in the animal world. On average, they reach a diameter of 1 mm - 50 times larger than that of most mammals - and they conduct excitation at a speed 25 m/s. And a three-meter squid dosidicus(it lives off the coast of Chile) the thickness of the nerves is fantastically large - 18 mm. Nerves are thick like ropes! Brain signals - the exciters of contractions - rush along the squid's nervous "freeway" at the speed of a car - 90 km/h.

Thanks to squids, research into the vital functions of nerves advanced rapidly at the beginning of the 20th century. "And who knows, writes British naturalist Frank Lane, maybe there are people now who owe the squid the fact that they nervous system is in good condition..."

The speed and maneuverability of the squid is also explained by its excellent hydrodynamic forms animal body, why squid and nicknamed “living torpedo”.

Squid(Teuthoidea), suborder cephalopods order of decapods. The size is usually 0.25-0.5 m, but some species are largest invertebrate animals(squids of the genus Architeuthis reach 18 m, including the length of the tentacles).
The body of squids is elongated, pointed at the back, torpedo-shaped, which determines their high speed of movement as in water ( up to 70 km/h), and in the air (squids can jump out of the water to a height up to 7 m).

Squid Jet Engine

Jet propulsion , now used in torpedoes, aircraft, missiles and space shells, is also characteristic of cephalopods - octopuses, cuttlefish, squids. Of greatest interest to technicians and biophysicists is squid jet engine. Notice how simply, with what minimal use of material, nature solved this complex and still unsurpassed task;-)

In essence, the squid has two fundamentally different engines ( rice. 1a). When moving slowly, it uses a large diamond-shaped fin, which periodically bends in the form of a running wave along the body of the body. The squid uses a jet engine to launch itself quickly.. The basis of this engine is the mantle - muscle tissue. It surrounds the mollusk’s body on all sides, making up almost half the volume of its body, and forms a kind of reservoir - mantle cavity - the “combustion chamber” of a living rocket, into which water is periodically sucked in. The mantle cavity contains gills and internal organs squid ( rice. 1b).

With a jet swimming method the animal sucks water through a wide open mantle gap into the mantle cavity from the boundary layer. The mantle gap is tightly “fastened” with special “cufflinks-buttons” after the “combustion chamber” of a living engine is filled with sea water. The mantle gap is located near the middle of the squid's body, where it is thickest. The force causing the movement of the animal is created by throwing a stream of water through a narrow funnel, which is located on the abdominal surface of the squid. This funnel, or siphon, is "nozzle" of a living jet engine.

The engine “nozzle” is equipped with a special valve and the muscles can turn it. By changing the angle of installation of the funnel-nozzle ( rice. 1c), the squid swims equally well both forward and backward (if it swims backward, the funnel is extended along the body, and the valve is pressed against its wall and does not interfere with the water stream flowing from the mantle cavity; when the squid needs to move forward, the free end of the funnel elongates somewhat and bends in the vertical plane, its outlet collapses and the valve takes a curved position). Jet shocks and the absorption of water into the mantle cavity follow one after another with elusive speed, and the squid rushes like a rocket in the blue of the ocean.

Squid and its jet engine - Figure 1

1a) squid – live torpedo; 1b) squid jet engine; 1c) the position of the nozzle and its valve when the squid moves back and forth.

The animal spends a fraction of a second taking water in and pushing it out. By sucking water into the mantle cavity in the aft part of the body during periods of slow movements due to inertia, the squid thereby carries out suction of the boundary layer, thus preventing the flow from stalling during an unsteady flow regime. By increasing the portions of ejected water and increasing the contraction of the mantle, the squid easily increases its speed of movement.

The squid jet engine is very economical, thanks to which he can reach speed 70 km/h; some researchers believe that even 150 km/h!

Engineers have already created engine similar to a squid jet engine: This water cannon, operating using a conventional gasoline or diesel engine. Why squid jet engine still attracts the attention of engineers and is the object of careful research by biophysicists? To work underwater, it is convenient to have a device that works without access atmospheric air. The creative search of engineers is aimed at creating a design hydrojet engine, similar air-jet…

Based on materials from wonderful books:
“Biophysics in physics lessons” Cecilia Bunimovna Katz,
And "Primates of the Sea" Igor Ivanovich Akimushkina

Kondakov Nikolay Nikolaevich (1908–1999) – Soviet biologist, animal artist, Candidate of Biological Sciences. Main contribution to biological science the drawings he made became various representatives fauna. These illustrations were included in many publications, such as Great Soviet Encyclopedia, Red Book of the USSR, in animal atlases and teaching aids.

Akimushkin Igor Ivanovich (01.05.1929–01.01.1993) – Soviet biologist, writer and popularizer of biology, author of popular science books about animal life. Laureate of the All-Union Society "Knowledge" award. Member of the USSR Writers' Union. The most famous publication of Igor Akimushkin is a six-volume book "Animal World".

The materials in this article will be useful to apply not only in physics lessons And biology, but also in extracurricular activities.
Biophysical material is extremely beneficial for mobilizing the attention of students, for turning abstract formulations into something concrete and close, affecting not only the intellectual, but also the emotional sphere.

Literature:
§ Katz Ts.B. Biophysics in physics lessons

§ § Akimushkin I.I. Primates of the sea
Moscow: Mysl Publishing House, 1974
§ Tarasov L.V. Physics in nature
Moscow: Prosveshchenie Publishing House, 1988

>>Physics: Jet propulsion

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 lightest touch, bounce off the stalk and from the hole formed at the site of the detached stalk, a bitter liquid with seeds is forcefully thrown out, while the cucumbers themselves fly off into 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. 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 payload(i.e. scientific equipment, the body of a spacecraft launched into orbit, the crew and the life support system of the ship).

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 gas stream high speed is thrown out of the rocket, 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:
F" = F (12.1)
Force F" (which is called reactive force) accelerates the rocket.

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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.

The 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 types 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, rapidly squeezing water out of it, can move in different sides.

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 ocean depths. Squids have achieved the highest perfection in jet navigation. They even have their own bodies 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 into reverse side. 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 horse.

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 a 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 in the sea with average speed 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.

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 rocket engine design based on liquid fuel, proposed a multi-stage rocket design, 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 engine is an engine that converts the chemical energy of fuel into kinetic energy gas jet, while the engine acquires speed in the opposite direction.

The idea of K.E. Tsiolkovsky was implemented by Soviet scientists under the leadership of Academician Sergei Pavlovich Korolev. The first artificial Earth satellite in history was launched by rocket in the Soviet Union on October 4, 1957.

The principle of jet propulsion is widely used practical application in aviation and astronautics. In outer space there is no medium with which a body could interact and thereby change the direction and magnitude of its speed, therefore only jets can be used for space flights aircraft, i.e. rockets.

Rocket device

The motion of a rocket is based on the law of conservation of momentum. If at some point in time any body is thrown away from the rocket, it will acquire the same impulse, but directed in the opposite direction

Any rocket, regardless of its design, always has a shell and fuel with an oxidizer. The rocket shell includes the payload (in this case a spacecraft), the instrument compartment and the engine (combustion chamber, pumps, etc.).

The main mass of the rocket is fuel with an oxidizer (the oxidizer is needed to maintain fuel combustion, since there is no oxygen in space).

Fuel and oxidizer are supplied to the combustion chamber using pumps. Fuel, when burned, turns into gas high temperature And high pressure. Due to the large pressure difference in the combustion chamber and in outer space, gases from the combustion chamber rush out in a powerful jet through the bell special form, called a nozzle. The purpose of the nozzle is to increase the speed of the jet.

Before the rocket launches, its momentum is zero. As a result of the interaction of the gas in the combustion chamber and all other parts of the rocket, the gas escaping through the nozzle receives some impulse. Then the rocket is a closed system, and its total momentum must be zero after launch. Therefore, the entire shell of the rocket that is in it receives an impulse equal in magnitude to the impulse of the gas, but opposite in direction.

The most massive part of the rocket, intended for launch and acceleration of the entire rocket, is called the first stage. When the first massive stage of a multi-stage rocket exhausts all its fuel reserves during acceleration, it separates. Further acceleration is continued by the second, less massive stage, and it adds some more speed to the speed previously achieved with the help of the first stage, and then separates. The third stage continues to increase speed to the required value and delivers the payload into orbit.

The first person to fly in outer space, was a citizen Soviet Union Yuri Alekseevich Gagarin. April 12, 1961 It flew around globe on the satellite ship "Vostok"

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 spaceship Vega 1 and Vega 2 closely examined Halley's Comet, which approaches the Sun once every 76 years.

Systems. Technique physical exercise. Target result movement depends not... Health powers nature Health powers nature provide significant influence...a combination of inertial forces, reactive and concentrated muscle contractions...

Jet propulsion.

But not a single scientist, not a single science fiction writer for many centuries could name the only means at a person’s disposal with which one can overcome the force of gravity and fly into space. This was accomplished by the Russian scientist Konstantin Eduardovich Tsiolkovsky (1857-1935). 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.

A jet engine is an engine that converts the chemical energy of fuel into the kinetic energy of a gas jet, and the engine acquires speed in the opposite direction. On what principles and physical laws is its action based?

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 great strength The recoil is felt by our shoulder, the stronger the reaction of the gun, the greater the reactive force. This is easy to explain from the law of conservation of momentum, which states that the geometric (i.e. vector) sum of the momentum of the bodies that make up a closed system remains constant for any movements and interactions of the bodies of the system.

K. E. Tsiolkovsky derived a formula that allows you to calculate maximum speed, which the rocket can develop.

The maximum achievable speed depends primarily on the speed of gas flow from the nozzle, which in turn depends primarily on the type of fuel and the temperature of the gas jet. The higher the temperature, the greater the speed. This means that for a rocket you need to select the most high-calorie fuel that gives greatest number warmth. The ratio of the mass of fuel to the mass of the rocket at the end of engine operation (that is, essentially to the weight of the empty rocket) is called the Tsiolkovsky number.

The main conclusion is that in airless space a rocket will develop a higher speed, the greater the speed of gas outflow and the larger number Tsiolkovsky.

Movements of bodies of variable mass.
Knowledge of the law of conservation of momentum in many cases makes it possible to find the result of the interaction of bodies when the values of the acting forces are unknown.

Let's take the action of a jet engine as an example. When fuel burns in the combustion chamber of a rocket, gases are formed that are heated to a high temperature. When the engine operates for a short time interval t, hot gases with a mass m are ejected from the rocket nozzle at a speed u relative to the rocket. The rocket and the gases emitted by its engine interact with each other. Based on the law of conservation of momentum, in the absence of external forces, the sum of the momentum vectors of interacting bodies remains constant.

Before the engines started operating, the momentum of the rocket and fuel was zero, therefore, even after switching on, the sum of changes in the vectors of the rocket momentum and the momentum of the exhaust gases is zero:

where m is the mass of the rocket, V is the change in the speed of the rocket, m is the mass of ejected gases, u is the velocity of the gases.

From here we get for the momentum vectors:

Let us divide both sides of the equality by the time interval t during which the rocket engines operated:

The product of the rocket's mass m and its acceleration a is, by definition, equal to the force causing this acceleration:

Thus, we have shown that the reactive thrust Fp is equal to the product of the speed u of the movement of the ejected gases relative to the rocket and the second fuel consumption m/t.

The reactive thrust force Fp acts from the side of the gases on the rocket and is directed in the direction opposite to the direction of the outflow of gases.

Expression

there is an equation for the dynamics of a body of variable mass for the case when external forces are equal to zero. If, in addition to the reactive force Fp, the rocket is acted upon by an external force F, then the equation of motion dynamics will take the form:

This equation was obtained by a professor at St. Petersburg University
I.V. Meshchersky and bears his name.

Meshchersky's formula is a generalization of Newton's second law for the motion of bodies of variable mass. The acceleration of a body of variable mass is determined not only by the external forces F acting on the body, but also by the reactive force Fp caused by the change in the mass of the moving body:

Rocket. Two body system. Fuel housing.
The housing is a pipe with one open end for the exhaust gases to escape. Nozzles (tubes) are installed on the tail for the directed release of gases at high speed.
Fuel is a complex fuel that, when burned, turns into a gas of high temperature and high movement.

V of a rocket depends on m of the fuel and the rocket itself, as well as on V of gas emissions.

This formula does not take into account air resistance and F to the Earth.

In fact, the release of gases does not occur instantly, but gradually. If we take into account all the conditions, then we need to take many times more fuel.

To give the ship the first escape velocity, then

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

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 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, compared to the animal itself, has a very large sizes, then its slight movement is enough for the squid, even at full speed ahead, could 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 horse.

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.

Application of jet propulsion in technology

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. Later he developed a scheme rocket engine on liquid fuel, 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 engine is an engine that converts the chemical energy of fuel into the kinetic energy of a gas jet, while the engine acquires speed in the opposite direction.

The principle of jet propulsion finds wide practical application in aviation and astronautics. In outer space there is no medium with which a body could interact and thereby change the direction and magnitude of its speed, therefore only jet aircraft, i.e., rockets, can be used for space flights.

Rocket device

The main mass of the rocket is fuel with an oxidizer (the oxidizer is needed to maintain fuel combustion, since there is no oxygen in space).

Fuel and oxidizer are supplied to the combustion chamber using pumps. Fuel, when burned, turns into a gas of high temperature and high pressure. Due to the large pressure difference in the combustion chamber and in outer space, gases from the combustion chamber rush out in a powerful jet through a specially shaped socket called a nozzle. The purpose of the nozzle is to increase the speed of the jet.

The most massive part of the rocket, intended for launch and acceleration of the entire rocket, is called the first stage. When the first massive step multistage rocket exhausts all fuel reserves during acceleration, it separates. Further acceleration is continued by the second, less massive stage, and it adds some more speed to the speed previously achieved with the help of the first stage, and then separates. The third stage continues to increase speed to the required value and delivers the payload into orbit.

The first person to fly in outer space was a citizen of the Soviet Union, Yuri Alekseevich Gagarin. April 12, 1961 He circled the globe on the Vostok satellite.

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.