Today, most people, of course, associate jet propulsion primarily with the latest scientific and technical developments. From textbooks on physics, we know that by "reactive" they mean the movement that occurs as a result of separation from an object (body) of any of its parts. A man wanted to rise into the sky to the stars, he strove to fly, but he could fulfill his dream only with the advent of jet aircraft and stepped spacecraft capable of traveling great distances, accelerating to supersonic speeds, thanks to modern jet engines installed on them. Designers and engineers developed the possibility of using jet propulsion in engines. Fantasts also did not stand aside, offering the most incredible ideas and ways to achieve this goal. Surprisingly, this principle of movement is widespread in wildlife. It is enough to look around, you can notice the inhabitants of the seas and land, among which there are plants, the basis of which is the reactive principle.

Story

Even in ancient times, scientists with interest studied and analyzed the phenomena associated with jet propulsion in nature. One of the first to theoretically substantiate and describe its essence was Heron, a mechanic and theorist of Ancient Greece, who invented the first steam engine named after him. The Chinese were able to find a practical application for the jet method. They were the first, taking as a basis the method of movement of cuttlefish and octopuses, back in the 13th century they invented rockets. They were used in fireworks, making a big impression, and also as flares, there may have been live rockets that were used as rocket artillery. Over time, this technology came to Europe.

N. Kibalchich became the discoverer of the new time, having invented a scheme for a prototype aircraft with a jet engine. He was an outstanding inventor and a convinced revolutionary, for which he was in prison. It was while in prison that he made history by creating his project. After his execution for active revolutionary activity and speaking out against the monarchy, his invention was forgotten on the archive shelves. Some time later, K. Tsiolkovsky was able to improve the ideas of Kibalchich, proving the possibility of exploring outer space through the jet movement of spacecraft.

Later, during the Great Patriotic War, the famous Katyushas, ​​field rocket artillery systems, appeared. So the affectionate name of the people unofficially referred to the powerful installations that were used by the forces of the USSR. It is not known for certain, in connection with which, the weapon received this name. The reason for this was either the popularity of Blanter's song, or the letter "K" on the body of the mortar. Over time, the front-line soldiers began to give nicknames to other weapons, thus creating a new tradition. The Germans, on the other hand, called this combat rocket launcher the “Stalinist organ” for its appearance, which resembled a musical instrument and the piercing sound that came from the launching rockets.

Vegetable world

Representatives of the fauna also use the laws of jet propulsion. Most of the plants with such properties are annuals and juveniles: prickly, petiolate garlic, heart touchy, double-cut pikulnik, three-veined mehringia.

Prickly, otherwise mad cucumber, belongs to the gourd family. This plant reaches a large size, has a thick root with a rough stem and large leaves. It grows in the territory of Central Asia, the Mediterranean, the Caucasus, is quite common in the south of Russia and Ukraine. Inside the fruit, during the ripening period, the seeds are converted into mucus, which, under the influence of temperatures, begins to ferment and release gas. Closer to ripening, the pressure inside the fetus can reach 8 atmospheres. Then, with a light touch, the fruit breaks off from the base and the seeds with liquid fly out of the fruit at a speed of 10 m/s. Due to the ability to shoot at 12 m in length, the plant was called the "lady's gun".

The heart of the touchy is an annual widespread species. It is found, as a rule, in shady forests, along the banks along rivers. Once in the northeastern part of North America and in South Africa, it successfully took root. The touchy heart is propagated by seeds. The seeds at the touchy core are small, weighing no more than 5 mg, which are thrown to a distance of 90 cm. Thanks to this method of seed distribution, the plant got its name.

Animal world

Jet propulsion - interesting facts about the animal world. In cephalopods, reactive movement occurs through water exhaled through a siphon, which usually narrows to a small opening to obtain maximum exhalation velocity. Water passes through the gills before exhalation, fulfilling the dual purpose of respiration and locomotion. Sea hares, otherwise gastropods, use similar means of locomotion, but without the complex neurological apparatus of cephalopods, they move more clumsily.

Some knightfish have also evolved jet propulsion by forcing water over their gills to supplement their fin propulsion.

In dragonfly larvae, reactive power is achieved by displacing water from a specialized cavity in the body. Scallops and cardids, siphonophores, tunics (such as salps), and some jellyfish also use jet propulsion.

Most of the time, scallops lie quietly on the bottom, but in case of danger, they quickly close the valves of their shells, so they push out the water. This behavior mechanism also speaks of the use of the principle of jet displacement. Thanks to him, the scallops can float up and move a long distance using the shell opening-closing technique.

The squid also uses this method, absorbing water, and then pushing it through the funnel with great force, it moves at a speed of at least 70 km / h. Gathering the tentacles into one knot, the body of the squid forms a streamlined shape. Taking such a squid engine as a basis, the engineers designed a water cannon. The water in it is sucked into the chamber, and then thrown out through the nozzle. Thus, the vessel is directed in the opposite direction from the ejected jet.

Compared to squids, salps use the most efficient engines, spending an order of magnitude less energy than squids. When moving, the salpa launches water into the hole in front, and then enters a wide cavity where the gills are stretched. After a sip, the hole closes, and with the help of contracting longitudinal and transverse muscles that compress the body, water is ejected through the hole from behind.

The most unusual of all the mechanisms of movement boasts an ordinary cat. Marcel Desprez suggested that the body is able to move and change its position even with the help of internal forces alone (without repelling or relying on anything), from which it could be concluded that Newton's laws could be wrong. The proof of his assumption could serve as a cat that fell from a height. During the fall upside down, she will still land on all her paws, this has already become a kind of axiom. Having photographed in detail the movement of the cat, we were able to see everything that she was doing in the air frame by frame. We saw her movement with her paw, which caused a response of the body, turning in the opposite direction relative to the movement of the paw. Acting according to Newton's laws, the cat landed successfully.

In animals, everything happens at the level of instinct, a person, in turn, does it consciously. Professional swimmers, having jumped from the tower, have time to turn around three times in the air, and having managed to stop the rotation, they straighten up strictly vertically and dive into the water. The same principle applies to aerial circus gymnasts.

No matter how much a person tries to surpass nature, improving the inventions created by it, anyway, we have not yet reached that technological perfection when airplanes could repeat the actions of a dragonfly: hover in the air, instantly move back or move to the side. And all this happens at high speed. Perhaps a little more time will pass and the aircraft, thanks to corrections for the aerodynamics and reactive capabilities of dragonflies, will be able to make sharp turns and become less susceptible to external conditions. Having peeped from nature, a person can still improve a lot for the benefit of technical progress.

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 ejects 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

In 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.

Jet propulsion, video

And finally, an entertaining video about physical experiments with jet propulsion.

The principle of jet motion is that this type of motion occurs when there is a separation at a certain speed from the body of its part. A classic example of jet propulsion is the movement of a rocket. The peculiarities of this movement include the fact that the body receives acceleration without interaction with other bodies. So, the movement of a rocket occurs due to a change in its mass. The mass of the rocket is reduced by the outflow of gases that occur during the combustion of fuel. Consider the motion of a rocket. Let's assume that the mass of the rocket is , and its speed at the moment of time is . After a while, the mass of the rocket decreases by a value and becomes equal to: , the speed of the rocket becomes equal to .

Then the change in momentum over time can be represented as:

where is the velocity of the outflow of gases with respect to the rocket. If we accept that is a small value of a higher order in comparison with the rest, then we get:

Under the action of external forces on the system (), we represent the change in momentum as:

We equate the right parts of formulas (2) and (3), we get:

where the expression - is called the reactive force. In this case, if the directions of the vectors and are opposite, then the rocket accelerates, otherwise it slows down. Equation (4) is called the equation of motion of a body of variable mass. It is often written in the form (I.V. Meshchersky's equation):

The idea of ​​using reactive power was proposed as early as the 19th century. Later K.E. Tsiolkovsky put forward the theory of rocket motion and formulated the foundations of the theory of a liquid-propellant jet engine. If we assume that external forces do not act on the rocket, then formula (4) will take the form:

>>Physics: Jet Propulsion

Newton's laws allow us to explain a very important mechanical phenomenon - jet propulsion. This is the name given to the movement of a body that occurs when a part of it separates from it at some speed.

Take, for example, a children's rubber balloon, inflate it and release it. We will see that when the air starts to leave it in one direction, the balloon itself will fly in the other direction. This is jet propulsion.

According to the principle of jet propulsion, some representatives of the animal world, such as squids and octopuses, move. Periodically throwing out the water they take in, 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, at the slightest touch, bounce off the stalk and from the hole formed in the place of the detached leg, a bitter liquid with seeds is ejected with force, while the cucumbers themselves fly off in the opposite direction.

The reactive motion that occurs when water is ejected can be observed in the following experiment. Let's pour water into a glass funnel connected to a rubber tube with an L-shaped tip (Fig. 20). We will see that when the water begins to pour out of the tube, the tube itself will begin to move and deviate in the direction opposite to the direction of the outflow 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 generated as a result of the combustion of fuel and ejected in the form of a jet stream) and the final or, as they say, "dry" mass of the rocket remaining after the ejection of the working fluid from the rocket.

The "dry" mass of the rocket, in turn, consists of the mass of the structure (i.e., the shell of the rocket, its engines and control system) and the mass of the payload (i.e., scientific equipment, the body of the spacecraft being launched into orbit, the crew and the system life support of the ship).

As the working fluid runs out, the empty tanks, excess parts of the shell, etc., begin to burden the rocket with unnecessary cargo, making it difficult to accelerate. Therefore, composite (or multi-stage) rockets are used to achieve cosmic velocities (Fig. 21). At first, only blocks of the first stage 1 work in such rockets. When the fuel supplies in them run out, they are separated and the second stage 2 is switched on; after the fuel is exhausted in it, it is also separated and the third stage 3 is turned on. The satellite or some 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 is flying in the Earth's atmosphere.

When a reactive gas jet 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:
F" = F (12.1)
Force F" (which is called reactive force) and accelerates the rocket.

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Among the great technical and scientific achievements of the 20th century, one of the first places undoubtedly belongs to rockets and jet propulsion theory. The years of the Second World War (1941-1945) led to an unusually rapid improvement in the design of jet vehicles. Gunpowder rockets reappeared on the battlefields, but already on more high-calorie smokeless TNT gunpowder (“Katyusha”). Jet-powered aircraft, unmanned aircraft with pulsed air-jet engines ("V-1") and ballistic missiles with a range of up to 300 km ("V-2") were created.

Rocket technology is now becoming a very important and rapidly growing branch of industry. The development of the theory of flight of jet vehicles is one of the pressing problems of modern scientific and technological development.

K. E. Tsiolkovsky did a lot for knowledge fundamentals of the theory of rocket motion. He was the first in the history of science to formulate and investigate the problem of studying rectilinear motions of rockets based on the laws of theoretical mechanics. As we have pointed out, the principle of communicating motion with the help of reaction forces of ejected particles was recognized by Tsiolkovsky as early as 1883, but his creation of a mathematically rigorous theory of jet propulsion dates back to the end of the 19th century.

In one of his works, Tsiolkovsky wrote: “For a long time I looked at the rocket, like everyone else: from the point of view of entertainment and small applications. I don't remember well how it occurred to me to do the calculations related to the rocket. It seems to me that the first seeds of thought were sown by the famous visionary Jules Verne; he awakened my brain in a certain direction. Desires appeared, behind the desires the activity of the mind arose. ... The old sheet with the final formulas related to the jet device is marked with the date August 25, 1898.

“... I never claimed to have a complete solution of the issue. First inevitably come: thought, fantasy, fairy tale. They are followed by scientific calculation. And in the end, the execution crowns the thought. My work on space travel belongs to the middle phase of creativity. More than anyone, I understand the abyss that separates an idea from its implementation, because during my life I not only thought and calculated, but also executed, also working with my hands. However, it is impossible not to be an idea: the execution is preceded by a thought, an exact calculation is a fantasy.

In 1903, the journal "Scientific Review" published the first article by Konstantin Eduardovich on rocketry, which was called "The study of world spaces by jet devices." In this work, on the basis of the simplest laws of theoretical mechanics (the law of conservation of momentum and the law of independent action of forces), a theory of rocket flight was given and the possibility of using jet vehicles for interplanetary communications was substantiated (The creation of a general theory of the motion of bodies whose mass changes in the process of motion belongs to Professor I. V. Meshchersky (1859-1935)).

The idea of ​​using a rocket to solve scientific problems, the use of jet engines to create the movement of grandiose interplanetary ships belong entirely to Tsiolkovsky. He is the founder of modern long-range liquid rockets, one of the creators of a new chapter in theoretical mechanics.

Classical mechanics, which studies the laws of motion and equilibrium of material bodies, is based on three laws of motion, clearly and strictly formulated by an English scientist back in 1687. These laws have been used by many researchers to study the motion of bodies whose mass did not change during the motion. Very important cases of motion were considered and a great science was created - the mechanics of bodies of constant mass. The axioms of the mechanics of bodies of constant mass, or Newton's laws of motion, were a generalization of all previous developments in mechanics. At present, the basic laws of mechanical motion are set forth in all physics textbooks for secondary schools. We will give here a summary of Newton's laws of motion, since the next step in science, which made it possible to study the motion of rockets, was a further development of the methods of classical mechanics.