Report: Jet propulsion in nature and technology. Interesting information about jet propulsion

This turntable can be called the world's first steam jet turbine.

Chinese rocket

Even earlier, many years before Heron of Alexandria, China also invented jet engine a slightly different device, now called fireworks rocket. Fireworks rockets should not be confused with their namesakes - signal rockets, which are used in the army and navy, and are also launched on national holidays under the roar of artillery fireworks. Flares are simply bullets compressed from a substance that burns with a colored flame. They are fired from large-caliber pistols - rocket launchers.

Flares are bullets compressed from a substance that burns with a colored flame.

Chinese rocket It is a cardboard or metal tube, closed at one end and filled with a powder composition. When this mixture is ignited, a stream of gases escaping at high speed from the open end of the tube causes the rocket to fly in the direction opposite to the direction of the gas stream. Such a rocket can take off without the help of a rocket launcher. A stick tied to the rocket body makes its flight more stable and straight.

Fireworks using Chinese rockets

Sea inhabitants

In the animal world:

Jet propulsion is also found here. Cuttlefish, octopuses and some other cephalopods have neither fins nor a powerful tail, but swim no worse than others sea ​​inhabitants. These soft-bodied creatures have a fairly capacious sac or cavity in their body. Water is drawn into the cavity, and then the animal pushes this water out with great force. The reaction of the ejected water causes the animal to swim in the direction opposite to the direction of the stream.

The octopus is a sea creature that uses jet propulsion

Falling cat

But the most interesting way of movement was demonstrated by the ordinary cat.

About a hundred and fifty years ago, a famous French physicist Marcel Depres stated:

But you know, Newton's laws are not entirely true. The body can move with the help of internal forces, without relying on anything or pushing away from anything.

Where is the evidence, where are the examples? - the listeners protested.

Want proof? If you please. A cat accidentally falling off a roof is proof! No matter how the cat falls, even head down, it will definitely stand on the ground with all four paws. But a falling cat does not rely on anything and does not push away from anything, but turns over quickly and deftly. (Air resistance can be neglected - it is too insignificant.)

Indeed, everyone knows this: cats, falling; always manage to get back on their feet.

Cats do this instinctively, but humans can do the same consciously. Swimmers who jump from a platform into the water know how to perform a complex figure - a triple somersault, that is, turn over three times in the air, and then suddenly straighten up, stop the rotation of their body and dive into the water in a straight line.

The same movements, without interaction with any foreign object, can be observed in the circus during the performance of acrobats - aerial gymnasts.

Performance of acrobats - aerial gymnasts

The falling cat was photographed with a film camera and then on the screen they examined, frame by frame, what the cat does when it flies in the air. It turned out that the cat was quickly twirling its paw. The rotation of the paw causes a response movement of the entire body, and it turns in the direction opposite to the movement of the paw. Everything happens in strict accordance with Newton's laws, and it is thanks to them that the cat gets on its feet.

The same thing happens in all cases where a living creature, without any apparent reason, changes its movement in the air.

Jet boat

The inventors had an idea, why not adopt their swimming method from cuttlefish. They decided to build a self-propelled ship with jet engine. The idea is definitely feasible. True, there was no confidence in success: the inventors doubted whether such a thing would turn out jet boat better than a regular screw. It was necessary to do an experiment.

Jet boat - a self-propelled vessel with a jet engine

They selected an old tug steamer, repaired its hull, removed the propellers, and installed a water jet pump in the engine room. This pump pumped sea water and through a pipe pushed it behind the stern with a strong jet. The steamer floated, but it still moved slower than the screw steamer. And this is explained simply: an ordinary propeller rotates behind the stern, unconstrained, with only water around it; The water in the water-jet pump was driven by almost exactly the same screw, but it no longer rotated on the water, but in a tight pipe. Friction of the water jet against the walls occurred. Friction weakened the pressure of the jet. A steamship with a water-jet propulsion sailed slower than a screw-propelled one and consumed more fuel.

However, they did not abandon the construction of such steamers: they had important advantages. A boat equipped with a propeller must sit deep in the water, otherwise the propeller will uselessly foam the water or spin in the air. Therefore, screw steamers are afraid of shallows and riffles; they cannot sail in shallow water. And water-jet steamers can be built shallow-draft and flat-bottomed: they don’t need depth - where the boat goes, the water-jet steamer will go.

The first water-jet boats in the Soviet Union were built in 1953 at the Krasnoyarsk shipyard. They are designed for small rivers where ordinary steamboats cannot navigate.

Engineers, inventors and scientists began to study jet propulsion especially diligently when firearms. The first guns - all kinds of pistols, muskets and self-propelled guns - hit a person hard in the shoulder with each shot. After several dozen shots, the shoulder began to hurt so much that the soldier could no longer aim. The first cannons - squeaks, unicorns, culverins and bombards - jumped back when fired, so that it happened that the gunners-artillerymen were crippled if they did not have time to dodge and jump to the side.

The recoil of the gun interfered with accurate shooting, because the gun flinched before the cannonball or grenade left the barrel. This threw off the lead. The shooting turned out to be aimless.

Shooting with firearms

Ordnance engineers began combating recoil more than four hundred and fifty years ago. First, the carriage was equipped with a coulter, which crashed into the ground and served as a strong support for the gun. Then they thought that if the gun was properly supported from behind, so that there was nowhere for it to roll away, then the recoil would disappear. But it was a mistake. The law of conservation of momentum was not taken into account. The guns broke all the supports, and the carriages became so loose that the gun became unsuitable for combat work. Then the inventors realized that the laws of motion, like any laws of nature, cannot be remade in their own way, they can only be “outwitted” with the help of science - mechanics.

They left a relatively small opener at the carriage for support, and placed the cannon barrel on a “sled” so that only one barrel rolled away, and not the entire gun. The barrel was connected to a compressor piston, which moves in its cylinder in the same way as a steam engine piston. But in the cylinder of a steam engine there is steam, and in a gun compressor there is oil and a spring (or compressed air).

When the gun barrel rolls back, the piston compresses the spring. At this time, the oil is forced through small holes in the piston on the other side of the piston. Strong friction occurs, which partially absorbs the movement of the rolling barrel, making it slower and smoother. Then the compressed spring straightens and returns the piston, and with it the gun barrel, to its original place. The oil presses on the valve, opens it and flows freely back under the piston. During rapid fire, the gun barrel moves almost continuously back and forth.

In a gun compressor, recoil is absorbed by friction.

Muzzle brake

When the power and range of the guns increased, the compressor was not enough to neutralize the recoil. It was invented to help him muzzle brake.

The muzzle brake is just a short steel pipe mounted on the end of the barrel and serves as its continuation. Its diameter is larger than the diameter of the barrel, and therefore it does not in any way interfere with the projectile flying out of the barrel. Several oblong holes are cut around the circumference of the tube walls.

Muzzle brake - reduces firearm recoil

Powder gases flying out of the gun barrel following the projectile immediately diverge to the sides, and some of them fall into the holes of the muzzle brake. These gases hit the walls of the holes with great force, are repelled from them and fly out, but not forward, but slightly askew and backward. At the same time, they press forward on the walls and push them, and with them the entire barrel of the gun. They help the fire monitor because they tend to cause the barrel to roll forward. And while they were in the barrel, they pushed the gun back. The muzzle brake significantly reduces and dampens recoil.

Other inventors took a different path. Instead of fighting reactive movement of the barrel and try to extinguish it, they decided to use the gun's rollback to good effect. These inventors created many types of automatic weapons: rifles, pistols, machine guns and cannons, in which the recoil serves to eject the spent cartridge case and reload the weapon.

Rocket artillery

You don’t have to fight recoil at all, but use it: after all, action and reaction (recoil) are equivalent, equal in rights, equal in magnitude, so let reactive action of powder gases, instead of pushing the gun barrel back, sends the projectile forward towards the target. This is how it was created rocket artillery. In it, a jet of gases hits not forward, but backward, creating a forward-directed reaction in the projectile.

For rocket gun the expensive and heavy barrel turns out to be unnecessary. A cheaper, simple iron pipe works perfectly to direct the flight of the projectile. You can do without a pipe at all, and make the projectile slide along two metal slats.

In its design, a rocket projectile is similar to a fireworks rocket, it is only larger in size. In its head part, instead of a composition for a colored sparkler, an explosive charge of great destructive power is placed. The middle of the projectile is filled with gunpowder, which, when burned, creates a powerful stream of hot gases that pushes the projectile forward. In this case, the combustion of gunpowder can last a significant part of the flight time, and not just the short period of time while an ordinary projectile advances in the barrel of an ordinary gun. The shot is not accompanied by such a loud sound.

Rocket artillery is no younger than ordinary artillery, and perhaps even older: ancient Chinese and Arabic books written more than a thousand years ago report on the combat use of rockets.

In descriptions of battles of later times, no, no, and there will be a mention of combat missiles. When British troops conquered India, Indian rocket warriors, with their fire-tailed arrows, terrified the British invaders who enslaved their homeland. For the British at that time, jet weapons were a novelty.

Rocket grenades invented by the general K. I. Konstantinov, the courageous defenders of Sevastopol in 1854-1855 repelled the attacks of the Anglo-French troops.

Rocket

The huge advantage over conventional artillery - there was no need to carry heavy guns - attracted the attention of military leaders to rocket artillery. But an equally major drawback prevented its improvement.

The fact is that the propelling charge, or, as they used to say, the force charge, could only be made from black powder. And black powder is dangerous to handle. It happened that during production missiles the propellant exploded and the workers died. Sometimes the rocket exploded upon launch, killing the gunners. Making and using such weapons was dangerous. That's why it hasn't become widespread.

The work that began successfully, however, did not lead to the construction of an interplanetary spacecraft. The German fascists prepared and unleashed a bloody world war.

Missile

The shortcomings in the production of rockets were eliminated by Soviet designers and inventors. During the Great Patriotic War they gave our army excellent rocket weapons. Guards mortars were built - "Katyusha" and RS ("eres") were invented - rockets.

Missile

In terms of quality, Soviet rocket artillery surpassed all foreign models and caused enormous damage to enemies.

Defending the Motherland, the Soviet people were forced to put all the achievements of rocket technology into the service of defense.

In fascist states, many scientists and engineers, even before the war, were intensively developing projects for inhumane weapons of destruction and mass murder. This they considered the purpose of science.

Self-driving aircraft

During the war, Hitler's engineers built several hundred self-driving aircraft: V-1 projectiles and V-2 rockets. These were cigar-shaped shells, 14 meters long and 165 centimeters in diameter. The deadly cigar weighed 12 tons; of which 9 tons are fuel, 2 tons are casing and 1 ton are explosives. "V-2" flew at speeds of up to 5,500 kilometers per hour and could rise to a height of 170-180 kilometers.

These means of destruction did not differ in hit accuracy and were only suitable for firing at such large targets as large and densely populated cities. The German fascists produced the V-2 200-300 kilometers from London in the belief that the city was large - it would hit somewhere!

It is unlikely that Newton could have imagined that his witty experience and the laws of motion he discovered would form the basis of weapons created by bestial anger towards people, and entire blocks of London would turn into ruins and become the graves of people captured by the raid of the blind “FAU”.

Spaceship

For many centuries, people have cherished the dream of flying in interplanetary space, of visiting the Moon, mysterious Mars and cloudy Venus. Many science fiction novels, novellas and short stories have been written on this topic. Writers sent their heroes into the sky on trained swans, in hot air balloons, in cannon shells, or in some other incredible way. However, all these methods of flight were based on inventions that had no support in science. People only believed that they would someday be able to leave our planet, but did not know how they would be able to do this.

Wonderful scientist Konstantin Eduardovich Tsiolkovsky in 1903 for the first time gave the scientific basis to the idea of ​​space travel. He proved that people can leave the globe and a rocket will serve as a vehicle for this, because a rocket is the only engine that does not need any external support for its movement. That's why rocket capable of flying in airless space.

Scientist Konstantin Eduardovich Tsiolkovsky proved that people can leave the globe on a rocket

In terms of its structure, the spacecraft should be similar to a rocket, only in its head there will be a cabin for passengers and instruments, and the rest of the space will be occupied by a supply of combustible mixture and an engine.

To give the ship the required speed, the right fuel is required. Gunpowder and other explosives are by no means suitable: they are both dangerous and burn too quickly, not providing long-term movement. K. E. Tsiolkovsky recommended using liquid fuel: alcohol, gasoline or liquefied hydrogen, burning in a stream of pure oxygen or some other oxidizing agent. Everyone recognized the correctness of this advice, because they did not know the best fuel at that time.

The first rocket with liquid fuel, weighing sixteen kilograms, was tested in Germany on April 10, 1929. The experimental rocket took off into the air and disappeared from view before the inventor and everyone present were able to trace where it flew. It was not possible to find the rocket after the experiment. The next time, the inventor decided to “outsmart” the rocket and tied a rope four kilometers long to it. The rocket took off, dragging its rope tail behind it. She pulled out two kilometers of rope, broke it and followed her predecessor in an unknown direction. And this fugitive also could not be found.

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"

The greatest interest is, perhaps, 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 blurry. 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 approximately 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.

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.

Below we will derive a simple differential equation that describes the motion of a body of variable mass, considering the flight of a rocket.

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.

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 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, 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 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 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 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 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 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.

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 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.