The effect of breaking the sound barrier. What is the sound barrier

What do we imagine when we hear the expression “sound barrier”? A certain limit can seriously affect hearing and well-being. Usually the sound barrier is correlated with the conquest of airspace and

Overcoming this obstacle can provoke the development of old diseases, pain syndromes and allergic reactions. Are these ideas correct or do they represent established stereotypes? Do they have a factual basis? What is the sound barrier? How and why does it arise? All this and some additional nuances, as well as historical facts We will try to find out what is associated with this concept in this article.

This mysterious science is aerodynamics

In the science of aerodynamics, designed to explain the phenomena accompanying movement
aircraft, there is a concept of “sound barrier”. This is a series of phenomena that occur during the movement of supersonic aircraft or rockets that move at speeds close to the speed of sound or greater.

What is a shock wave?

As a supersonic flow flows around a vehicle, a shock wave appears in a wind tunnel. Its traces can be visible even to the naked eye. On the ground they are expressed by a yellow line. Outside the shock wave cone, in front of the yellow line, you can’t even hear the plane on the ground. At speeds exceeding sound, bodies are subjected to a flow of sound flow, which entails a shock wave. There may be more than one, depending on the shape of the body.

Shock wave transformation

The shock wave front, which is sometimes called a shock wave, has a fairly small thickness, which nevertheless makes it possible to track abrupt changes in the properties of the flow, a decrease in its speed relative to the body and a corresponding increase in the pressure and temperature of the gas in the flow. In this case, the kinetic energy is partially converted into internal energy of the gas. The number of these changes directly depends on the speed of the supersonic flow. As the shock wave moves away from the apparatus, the pressure drops decrease and the shock wave is converted into a sound wave. It can reach an outside observer, who will hear a characteristic sound resembling an explosion. There is an opinion that this indicates that the device has reached the speed of sound, when the plane leaves the sound barrier behind.

What's really going on?

The so-called moment of breaking the sound barrier in practice represents the passage of a shock wave with the increasing roar of the aircraft engines. Now the device is ahead of the accompanying sound, so the hum of the engine will be heard after it. Approaching the speed of sound became possible during the Second World War, but at the same time pilots noted alarming signals in the operation of aircraft.

After the end of the war, many aircraft designers and pilots sought to reach the speed of sound and break the sound barrier, but many of these attempts ended tragically. Pessimistic scientists argued that this limit could not be exceeded. By no means experimental, but scientific, it was possible to explain the nature of the concept of “sound barrier” and find ways to overcome it.

Safe flights at transonic and supersonic speeds are possible by avoiding a wave crisis, the occurrence of which depends on the aerodynamic parameters of the aircraft and the altitude of the flight. Transitions from one speed level to another should be carried out as quickly as possible using afterburner, which will help to avoid a long flight in the wave crisis zone. The wave crisis as a concept came from water transport. It arose when ships moved at a speed close to the speed of waves on the surface of the water. Getting into a wave crisis entails difficulty in increasing speed, and if you overcome the wave crisis as simply as possible, then you can enter the mode of planing or sliding along the water surface.

History in aircraft control

The first person to reach supersonic flight speed in an experimental aircraft was the American pilot Chuck Yeager. His achievement was noted in history on October 14, 1947. On the territory of the USSR, the sound barrier was broken on December 26, 1948 by Sokolovsky and Fedorov, who were flying an experienced fighter.

Among civilians, the passenger airliner Douglas DC-8 broke the sound barrier, which on August 21, 1961 reached a speed of 1.012 Mach, or 1262 km/h. The purpose of the flight was to collect data for wing design. Among aircraft, the world record was set by a hypersonic air-to-ground aeroballistic missile, which is in service with the Russian army. At an altitude of 31.2 kilometers, the rocket reached a speed of 6389 km/h.

50 years after breaking the sound barrier in the air, Englishman Andy Green achieved a similar achievement in a car. American Joe Kittinger tried to break the record in free fall, reaching a height of 31.5 kilometers. Today, on October 14, 2012, Felix Baumgartner set a world record, without the help of transport, in a free fall from a height of 39 kilometers, breaking the sound barrier. Its speed reached 1342.8 kilometers per hour.

The most unusual breaking of the sound barrier

It’s strange to think, but the first invention in the world to overcome this limit was the ordinary whip, which was invented by the ancient Chinese almost 7 thousand years ago. Almost until the invention of instant photography in 1927, no one suspected that the crack of a whip was a miniature sonic boom. A sharp swing forms a loop, and the speed increases sharply, which is confirmed by the click. The sound barrier is broken at a speed of about 1200 km/h.

The mystery of the noisiest city

It’s no wonder that residents of small towns are shocked when they see the capital for the first time. The abundance of transport, hundreds of restaurants and entertainment centers confuse and unsettle you. The beginning of spring in the capital is usually dated to April, rather than the rebellious, blizzardy March. In April there are clear skies, streams are flowing and buds are blooming. People, tired from the long winter, open their windows wide towards the sun, and street noise bursts into their houses. Birds chirp deafeningly on the street, artists sing, cheerful students recite poetry, not to mention the noise in traffic jams and the subway. Hygiene department employees note that staying in a noisy city for a long time is harmful to health. The sound background of the capital consists of transport,
aviation, industrial and household noise. The most harmful is car noise, since planes fly quite high, and the noise from enterprises dissolves in their buildings. The constant hum of cars on particularly busy highways exceeds all acceptable standards twice. How does the capital overcome the sound barrier? Moscow is dangerous with an abundance of sounds, so residents of the capital install double-glazed windows to muffle the noise.

How is the sound barrier stormed?

Until 1947, there was no actual data on the well-being of a person in the cockpit of an airplane that flies faster than sound. As it turns out, breaking the sound barrier requires certain strength and courage. During the flight, it becomes clear that there is no guarantee of survival. Even a professional pilot cannot say for sure whether the aircraft’s design will withstand an attack from the elements. In a matter of minutes, the plane can simply fall apart. What explains this? It should be noted that movement at subsonic speed creates acoustic waves that spread out like circles from a fallen stone. Supersonic speed excites shock waves, and a person standing on the ground hears a sound similar to an explosion. Without powerful computers, it was difficult to solve complex problems and one had to rely on blowing models in wind tunnels. Sometimes, when the plane's acceleration is insufficient, the shock wave reaches such a force that windows fly out of the houses over which the plane flies. Not everyone will be able to overcome the sound barrier, because at this moment the entire structure shakes, and the mountings of the device can receive significant damage. That's why it's so important for pilots good health and emotional stability. If the flight is smooth and the sound barrier is overcome as quickly as possible, then neither the pilot nor any possible passengers will feel any particularly unpleasant sensations. A research aircraft was built specifically to break the sound barrier in January 1946. The creation of the machine was initiated by an order from the Ministry of Defense, but instead of weapons it was stuffed with scientific equipment that monitored the operating mode of mechanisms and instruments. This plane was like a modern cruise missile with a built-in rocket engine. The plane broke the sound barrier at a maximum speed of 2736 km/h.

Verbal and material monuments to conquering the speed of sound

Achievements in breaking the sound barrier are still highly valued today. So, the plane in which Chuck Yeager first overcame it is now on display at the National Air and Space Museum, which is located in Washington. But technical specifications this human invention would be worth little without the merits of the pilot himself. Chuck Yeager went through flight school and fought in Europe, after which he returned to England. The unfair exclusion from flying did not break Yeager’s spirit, and he achieved a reception with the commander-in-chief of the European troops. In the years remaining until the end of the war, Yeager took part in 64 combat missions, during which he shot down 13 aircraft. Chuck Yeager returned to his homeland with the rank of captain. His characteristics indicate phenomenal intuition, incredible composure and endurance in critical situations. More than once Yeager set records on his plane. His further career was in the Air Force units, where he trained pilots. IN last time Chuck Yeager broke the sound barrier at age 74, which was the fiftieth anniversary of his flight history and in 1997.

Complex tasks of aircraft creators

The world-famous MiG-15 aircraft began to be created at the moment when the developers realized that it was impossible to rely only on breaking the sound barrier, but that complex technical problems had to be solved. As a result, a machine was created so successful that its modifications entered service with different countries. Several different design bureaus entered into a kind of competitive struggle, the prize in which was a patent for the most successful and functional aircraft. Aircraft with swept wings were developed, which was a revolution in their design. The ideal device had to be powerful, fast and incredibly resistant to any external damage. The swept wings of airplanes became an element that helped them triple the speed of sound. Then it continued to increase, which was explained by an increase in engine power, the use of innovative materials and optimization of aerodynamic parameters. Overcoming the sound barrier has become possible and real even for a non-professional, but this does not make it any less dangerous, so any extreme sports enthusiast should sensibly assess their strengths before deciding to undertake such an experiment.

On October 14, 1947, humanity crossed another milestone. The limit is quite objective, expressed in a specific physical quantity - the speed of sound in air, which in the conditions of the earth's atmosphere is, depending on its temperature and pressure, within the range of 1100-1200 km/h. Supersonic speed was conquered by the American pilot Chuck Yeager (Charles Elwood "Chuck" Yeager), a young veteran of World War II, who had extraordinary courage and excellent photogenicity, thanks to which he immediately became popular in his homeland, just like 14 years later Yuri Gagarin.

And it really took courage to cross the sound barrier. Soviet pilot Ivan Fedorov, who repeated Yeager’s achievement a year later, in 1948, recalled his feelings at that time: “Before the flight to break the sound barrier, it became obvious that there was no guarantee of surviving after it. No one knew practically what it was and whether the aircraft’s design could withstand the elements. But we tried not to think about it.”

Indeed, there was no complete clarity as to how the car would behave at supersonic speed. The aircraft designers still had fresh memories of the sudden misfortune of the 30s, when, with the increase in aircraft speeds, they had to urgently solve the problem of flutter - self-oscillations that arise both in the rigid structures of the aircraft and in its skin, tearing the aircraft apart in a matter of minutes. The process developed like an avalanche, rapidly, the pilots did not have time to change the flight mode, and the machines fell apart in the air. For quite a long time mathematicians and designers have been in various countries struggled to solve this problem. In the end, the theory of the phenomenon was created by the then young Russian mathematician Mstislav Vsevolodovich Keldysh (1911–1978), later president of the USSR Academy of Sciences. With the help of this theory, it was possible to find a way to get rid of the unpleasant phenomenon forever.

It is quite clear that equally unpleasant surprises were expected from the sound barrier. Numerical solution of complex differential equations of aerodynamics in the absence of powerful computers was impossible, and one had to rely on “blowing” the models in wind tunnels. But from qualitative considerations it was clear that when the speed of sound was reached, a shock wave appeared near the aircraft. The most crucial moment is breaking the sound barrier, when the speed of the aircraft is compared to the speed of sound. At this moment, the pressure difference on different sides of the wave front quickly increases, and if the moment lasts longer than an instant, the plane can fall apart no worse than from flutter. Sometimes, when breaking the sound barrier with insufficient acceleration, the shock wave created by the aircraft even knocks out the glass from the windows of houses on the ground below it.

The ratio of an aircraft's speed to the speed of sound is called the Mach number (named after the famous German mechanic and philosopher Ernst Mach). When passing the sound barrier, it seems to the pilot that the M number jumps over one in leaps and bounds: Chuck Yeager saw how the speedometer needle jumped from 0.98 to 1.02, after which there was “divine” silence in the cockpit in fact, apparent: just a level The sound pressure in the aircraft cabin drops several times. This moment of “purification from sound” is very insidious; it cost the lives of many testers. But there was little danger of his X-1 aircraft falling apart.

The X-1, manufactured by Bell Aircraft in January 1946, was a purely research aircraft designed to break the sound barrier and nothing more. Despite the fact that the vehicle was ordered by the Ministry of Defense, instead of weapons it was stuffed with scientific equipment that monitors the operating modes of components, instruments and mechanisms. The X-1 was like a modern cruise missile. It had one Reaction Motors rocket engine with a thrust of 2722 kg. Maximum take-off weight 6078 kg. Length 9.45 m, height 3.3 m, wingspan 8.53 m. Maximum speed at an altitude of 18290 m 2736 km/h. The vehicle was launched from a B-29 strategic bomber and landed on steel “skis” on a dry salt lake.

The “tactical and technical parameters” of its pilot are no less impressive. Chuck Yeager was born on February 13, 1923. After school I went to flight school, and after graduating I went to fight in Europe. Shot down one Messerschmitt-109. He himself was shot down in the skies of France, but was saved by partisans. As if nothing had happened, he returned to his base in England. However, the vigilant counterintelligence service, not believing the miraculous release from captivity, removed the pilot from flying and sent him to the rear. The ambitious Yeager achieved a reception with the commander-in-chief of the Allied forces in Europe, General Eisenhower, who believed Yeager. And he was not mistaken - in the six months remaining before the end of the war, he made 64 combat missions, shot down 13 enemy aircraft, 4 in one battle. And he returned to his homeland with the rank of captain with an excellent dossier, which stated that he had phenomenal flight intuition, incredible composure and amazing endurance in any situation. critical situation. Thanks to this characteristic, he was included in the team of supersonic testers, who were selected and trained as carefully as later astronauts.

Renaming the X-1 “Glamorous Glennis” in honor of his wife, Yeager set records with it more than once. At the end of October 1947, the previous altitude record of 21,372 m fell. In December 1953, a new modification of the machine, the X-1A, reached a speed of 2.35 M and almost 2800 km/h, and six months later rose to a height of 27,430 m. And before In addition, there were tests of a number of fighters launched into series and testing of our MiG-15, captured and transported to America during Korean War. Yeager subsequently commanded various Air Force test units both in the United States and at American bases in Europe and Asia, took part in combat operations in Vietnam, and trained pilots. He retired in February 1975 with the rank of brigadier general, having flown 10 thousand hours during his valiant service, tested 180 different supersonic models and collected a unique collection of orders and medals. In the mid-80s, a film was made based on the biography of the brave guy who was the first in the world to conquer the sound barrier, and after that Chuck Yeager became not even a hero, but a national relic. He flew an F-16 for the last time on October 14, 1997, breaking the sound barrier on the fiftieth anniversary of his historic flight. Yeager was then 74 years old. In general, as the poet said, these people should be made into nails.

There are many such people on the other side of the ocean Soviet designers began to try to conquer the sound barrier at the same time as American ones. But for them this was not an end in itself, but a completely pragmatic act. If the X-1 was a purely research machine, then in our country the sound barrier was stormed on prototype fighters, which were supposed to be launched into series to equip Air Force units.

Several design bureaus took part in the competition: Lavochkin Design Bureau, Mikoyan Design Bureau and Yakovlev Design Bureau, which simultaneously developed aircraft with swept wings, which was then a revolutionary design solution. They reached the supersonic finish in this order: La-176 (1948), MiG-15 (1949), Yak-50 (1950). However, there the problem was solved in a rather complex context: a military vehicle must have not only high speed, but also many other qualities - maneuverability, survivability, minimal pre-flight preparation time, powerful weapons, impressive ammunition, etc. and so on. It should also be noted that in Soviet times, the decisions of state acceptance commissions were often influenced not only by objective factors, but also by subjective factors associated with the political maneuvers of developers. This whole set of circumstances led to the launch of the MiG-15 fighter, which performed well in the local arenas of military operations in the 50s. It was this car, captured in Korea, as mentioned above, that Chuck Yeager “drove around.”

The La-176 used a record sweep of the wing at that time, equal to 45 degrees. The VK-1 turbojet engine provided a thrust of 2700 kg. Length 10.97 m, wingspan 8.59 m, wing area 18.26 sq.m. Take-off weight 4636 kg. Ceiling 15,000 m. Flight range 1000 km. Armament one 37 mm cannon and two 23 mm. The car was ready in the fall of 1948, and in December its flight tests began in Crimea at a military airfield near the city of Saki. Among those who led the tests was the future academician Vladimir Vasilyevich Struminsky (1914–1998); the pilots of the experimental aircraft were captain Oleg Sokolovsky and colonel Ivan Fedorov, who later received the title of Hero Soviet Union. Sokolovsky, by an absurd accident, died during the fourth flight, having forgotten to close the cockpit canopy.

Colonel Ivan Fedorov broke the sound barrier on December 26, 1948. Having risen to a height of 10 thousand meters, he turned the control stick away from himself and began to accelerate in a dive. “I’m accelerating my 176 from a great height,” the pilot recalled. A tedious low whistle is heard. Increasing speed, the plane rushes towards the ground. On the speedometer scale, the needle moves from three-digit numbers to four-digit numbers. The plane is shaking as if in a fever. And suddenly silence! The sound barrier has been taken. Subsequent decoding of the oscillograms showed that the number M had exceeded one.” This happened at an altitude of 7,000 meters, where a speed of 1.02 M was recorded.

Subsequently, the speed of manned aircraft continued to steadily increase due to an increase in engine power, the use of new materials and optimization of aerodynamic parameters. However, this process is not unlimited. On the one hand, it is inhibited by considerations of rationality, when fuel consumption, development costs, flight safety and other not idle considerations are taken into account. And even in military aviation, where money and pilot safety are not so significant, the speeds of the most “fast” machines are in the range from 1.5M to 3M. It seems like no more is required. (The speed record for manned aircraft with jet engines belongs to the American reconnaissance aircraft SR-71 and is 3.2 M.)

On the other hand, there is an insurmountable thermal barrier: at a certain speed, heating of the car body by friction with air occurs so quickly that it is impossible to remove heat from its surface. Calculations show that at normal pressure this should occur at a speed of the order of 10 Mach.

Nevertheless, the 10M limit was still reached at the same Edwards training ground. This happened in 2005. The record holder was the X-43A unmanned rocket aircraft, manufactured as part of the 7-year ambitious Hiper-X program to develop a new type of technology designed to radically change the face of future rocket and space technology. Its cost is $230 million. The record was set at an altitude of 33 thousand meters. Used in a drone new system acceleration First, a traditional solid-fuel rocket is fired, with the help of which the X-43A reaches a speed of 7 Mach, and then a new type of engine is turned on - a hypersonic ramjet engine (scramjet, or scramjet), in which ordinary atmospheric air is used as an oxidizer, and gaseous fuel is used as an oxidizer. hydrogen (quite a classic scheme of an uncontrolled explosion).

In accordance with the program, three unmanned models were manufactured, which, after completing the task, were drowned in the ocean. The next stage involves the creation of manned vehicles. After testing them, the results obtained will be taken into account when creating a wide variety of “useful” devices. In addition to aircraft, hypersonic military vehicles - bombers, reconnaissance aircraft and transport aircraft - will be created for NASA's needs. Boeing, which is participating in the Hiper-X program, plans to create a hypersonic airliner for 250 passengers by 2030-2040. It is quite clear that the windows, which at such speeds break the aerodynamics and cannot withstand thermal heating, it won't be in it. Instead of portholes, there are screens with video recordings of passing clouds.

There is no doubt that this type of transport will be in demand, since the further you go, the more expensive time becomes, accommodating more and more emotions, dollars earned and other components of modern life into a unit of time. In this regard, there is no doubt that someday people will turn into one-day butterflies: one day will be as eventful as today’s (or rather, yesterday’s) human life. And it can be assumed that someone or something is implementing the Hiper-X program in relation to humanity.

Passed the sound barrier :-)...

Before we start talking about the topic, let's bring some clarity to the question of the accuracy of concepts (what I like :-)). Nowadays two terms are in fairly wide use: sound barrier And supersonic barrier . They sound similar, but still not the same. However, there is no point in being particularly strict: in essence, they are one and the same thing. The definition of sound barrier is most often used by people who are more knowledgeable and closer to aviation. And the second definition is usually everyone else.

I think that from the point of view of physics (and the Russian language :-)) it is more correct to say the sound barrier. There is simple logic here. After all, there is a concept of the speed of sound, but, strictly speaking, there is no fixed concept of supersonic speed. Looking ahead a little, I will say that when an aircraft flies at supersonic speed, it has already passed this barrier, and when it passes (overcomes) it, it then passes a certain threshold speed value equal to the speed of sound (and not supersonic).

Something like that:-). Moreover, the first concept is used much less frequently than the second. This is apparently because the word supersonic sounds more exotic and attractive. And in supersonic flight, the exotic is certainly present and, naturally, attracts many. However, not all people who savor the words “ supersonic barrier“They actually understand what it is. I have already been convinced of this more than once, looking at forums, reading articles, even watching TV.

This question is actually quite complex from a physics point of view. But, of course, we won’t bother with complexity. We’ll just try, as usual, to clarify the situation using the principle of “explaining aerodynamics on your fingers” :-).

So, to the barrier (sound :-))!... An airplane in flight, acting on such an elastic medium as air, becomes a powerful source of sound waves. I think everyone knows what sound waves in air are :-).

Sound waves (tuning fork).

This is an alternation of areas of compression and rarefaction, spreading in different directions from the sound source. Something like circles on water, which are also waves (just not sound ones :-)). It is these areas, acting on the eardrum of the ear, that allow us to hear all the sounds of this world, from human whispers to the roar of jet engines.

An example of sound waves.

The points of propagation of sound waves can be various components of the aircraft. For example, an engine (its sound is known to anyone :-)), or parts of the body (for example, the bow), which, compacting the air in front of them as they move, create a certain type of pressure (compression) wave running forward.

All these sound waves propagate in the air at the speed of sound already known to us. That is, if the plane is subsonic, and even flies at low speed, then they seem to run away from it. As a result, when such an aircraft approaches, we first hear its sound, and then it itself flies by.

I will make a reservation, however, that this is true if the plane is not flying very high. After all, the speed of sound is not the speed of light :-). Its magnitude is not so great and sound waves need time to reach the listener. Therefore, the order of sound appearance for the listener and the plane, if it flies high altitude can change.

And since the sound is not so fast, then with an increase in its own speed the plane begins to catch up with the waves it emits. That is, if he were motionless, then the waves would diverge from him in the form concentric circles like ripples on the water caused by a thrown stone. And since the plane is moving, in the sector of these circles corresponding to the direction of flight, the boundaries of the waves (their fronts) begin to approach each other.

Subsonic body movement.

Accordingly, the gap between the aircraft (its nose) and the front of the very first (head) wave (that is, this is the area where gradual, to a certain extent, braking occurs free stream when meeting with the nose of the aircraft (wing, tail) and, as a consequence, increase in pressure and temperature) begins to contract and the faster the higher the flight speed.

There comes a moment when this gap practically disappears (or becomes minimal), turning into a special kind of area called shock wave. This happens when the flight speed reaches the speed of sound, that is, the plane moves at the same speed as the waves it emits. The Mach number is equal to unity (M=1).

Sound movement of the body (M=1).

Shock shock, is a very narrow region of the medium (about 10 -4 mm), when passing through which there is no longer a gradual, but a sharp (jump-like) change in the parameters of this medium - speed, pressure, temperature, density. In our case, the speed decreases, pressure, temperature and density increase. Hence the name - shock wave.

In a somewhat simplified way, I would say this about all this. It is impossible to abruptly slow down a supersonic flow, but it has to do this, because there is no longer the possibility of gradual braking to the speed of the flow in front of the very nose of the aircraft, as at moderate subsonic speeds. It seems to come across a subsonic section in front of the nose of the aircraft (or the tip of the wing) and collapses into a narrow jump, transferring to it the great energy of movement that it possesses.

By the way, we can say the other way around: the plane transfers part of its energy to the formation of shock waves in order to slow down the supersonic flow.

Supersonic body movement.

There is another name for the shock wave. Moving with the aircraft in space, it essentially represents the front of a sharp change in the above-mentioned environmental parameters (that is, air flow). And this is the essence of a shock wave.

Shock shock and shock wave, in general, are equivalent definitions, but in aerodynamics the first one is more used.

The shock wave (or shock wave) can be practically perpendicular to the direction of flight, in which case they take approximately the shape of a circle in space and are called straight lines. This usually happens in modes close to M=1.

Body movement modes. ! - subsonic, 2 - M=1, supersonic, 4 - shock wave (shock wave).

At numbers M > 1, they are already located at an angle to the direction of flight. That is, the plane is already surpassing its own sound. In this case, they are called oblique and in space they take the shape of a cone, which, by the way, is called the Mach cone, named after a scientist who studied supersonic flows (mentioned him in one of them).

Mach cone.

The shape of this cone (its “slimness,” so to speak) depends precisely on the number M and is related to it by the relation: M = 1/sin α, where α is the angle between the axis of the cone and its generatrix. And the conical surface touches the fronts of all sound waves, the source of which was the plane, and which it “overtook”, reaching supersonic speed.

Besides shock waves may also be annexed, when they are adjacent to the surface of a body moving at supersonic speed, or moving away, if they are not in contact with the body.

Types of shock waves during supersonic flow around bodies of various shapes.

Usually shocks become attached if the supersonic flow flows around any pointed surfaces. For an airplane, for example, this could be a pointed nose, a high-pressure air intake, or a sharp edge of the air intake. At the same time they say “the jump sits”, for example, on the nose.

And a detached shock can occur when flowing around rounded surfaces, for example, the leading rounded edge of a thick airfoil of a wing.

Various components of the aircraft body create a rather complex system of shock waves in flight. However, the most intense of them are two. One is the head one on the bow and the second is the tail one on the tail elements. At some distance from the aircraft, the intermediate shocks either catch up with the head one and merge with it, or the tail one catches up with them.

Shock shocks on a model aircraft during purging in a wind tunnel (M=2).

As a result, two jumps remain, which, in general, are perceived by an earthly observer as one due to the small size of the aircraft compared to the flight altitude and, accordingly, the short period of time between them.

The intensity (in other words, energy) of a shock wave (shock wave) depends on various parameters (the speed of the aircraft, its design features, environmental conditions, etc.) and is determined by the pressure drop at its front.

As it moves away from the top of the Mach cone, that is, from the aircraft, as a source of disturbance, the shock wave weakens, gradually turns into an ordinary sound wave and ultimately disappears completely.

And on what degree of intensity it will have shock wave(or shock wave) reaching the ground depends on the effect it can produce there. It’s no secret that the well-known Concorde flew supersonic only over the Atlantic, and military supersonic aircraft reach supersonic speed at high altitudes or in areas where there are no settlements(at least it seems like they should do it :-)).

These restrictions are very justified. For me, for example, the very definition of a shock wave is associated with an explosion. And the things that a sufficiently intense shock wave can do may well correspond to it. At least the glass from the windows can easily fly out. There is enough evidence of this (especially in the history of Soviet aviation, when it was quite numerous and flights were intense). But you can do worse things. You just have to fly lower :-)…

However, for the most part, what remains of shock waves when they reach the ground is no longer dangerous. Just an outside observer on the ground can hear a sound similar to a roar or explosion. It is with this fact that one common and rather persistent misconception is associated.

People who are not too experienced in aviation science, hearing such a sound, say that the plane overcame sound barrier (supersonic barrier). Actually this is not true. This statement has nothing to do with reality for at least two reasons.

Shock wave (shock wave).

Firstly, if a person on the ground hears a loud roar high in the sky, then this only means (I repeat :-)) that his ears have reached shock wave front(or shock wave) from an airplane flying somewhere. This plane is already flying at supersonic speed, and has not just switched to it.

And if this same person could suddenly find himself several kilometers ahead of the plane, then he would again hear the same sound from the same plane, because he would be exposed to the same shock wave moving with the plane.

It moves at supersonic speed, and therefore approaches silently. And after it has had its not always pleasant effect on the eardrums (it’s good, when only on them :-)) and has safely passed on, the roar of running engines becomes audible.

An approximate flight diagram of an aircraft at various values of the Mach number using the example of the Saab 35 "Draken" fighter. The language, unfortunately, is German, but the scheme is generally clear.

Moreover, the transition to supersonic sound itself is not accompanied by any one-time “booms”, pops, explosions, etc. On a modern supersonic aircraft, the pilot most often learns about such a transition only from instrument readings. In this case, however, a certain process occurs, but it is subject to certain rules piloting is practically invisible to him.

But that's not all :-). I'll say more. in the form of some tangible, heavy, difficult-to-cross obstacle that the plane rests on and which needs to be “pierced” (I have heard such judgments :-)) does not exist.

Strictly speaking, there is no barrier at all. Once upon a time, at the dawn of the development of high speeds in aviation, this concept was formed rather as psychological belief about the difficulty of transitioning to supersonic speed and flying at it. There were even statements that this was generally impossible, especially since the prerequisites for such beliefs and statements were quite specific.

However, first things first...

In aerodynamics, there is another term that quite accurately describes the process of interaction with the air flow of a body moving in this flow and tending to go supersonic. This wave crisis. It is he who does some bad things that are traditionally associated with the concept sound barrier.

So something about the crisis :-). Any aircraft consists of parts, the air flow around which during flight may not be the same. Let's take, for example, a wing, or rather an ordinary classic subsonic profile.

From the basic knowledge of how lift is generated, we know well that the flow speed in the adjacent layer of the upper curved surface of the profile is different. Where the profile is more convex, it is greater than the overall flow velocity, then, when the profile is flattened, it decreases.

When the wing moves in the flow at speeds close to the speed of sound, a moment may come when in such a convex area, for example, the speed of the air layer, which is already greater than the total speed of the flow, becomes sonic and even supersonic.

Local shock wave that occurs at transonics during a wave crisis.

Further along the profile, this speed decreases and at some point again becomes subsonic. But, as we said above, a supersonic flow cannot quickly slow down, so the emergence of shock wave.

Such shocks appear in different areas of the streamlined surfaces, and initially they are quite weak, but their number can be large, and with an increase in the overall flow speed, the supersonic zones increase, the shocks “get stronger” and shift to the trailing edge of the profile. Later, the same shock waves appear on the lower surface of the profile.

Full supersonic flow around the wing profile.

What does all this mean? Here's what. First– this is significant increase in aerodynamic drag in the transonic speed range (about M=1, more or less). This resistance grows due to a sharp increase in one of its components - wave resistance. The same thing that we previously did not take into account when considering flights at subsonic speeds.

For the formation of numerous shock waves (or shock waves) during the deceleration of a supersonic flow, as I said above, energy is wasted, and it is taken from kinetic energy aircraft movements. That is, the plane simply slows down (and very noticeably!). That's what it is wave resistance.

Moreover, shock waves, due to the sharp deceleration of the flow in them, contribute to the separation of the boundary layer behind itself and its transformation from laminar to turbulent. This further increases aerodynamic drag.

Swelling of the profile when different numbers M. Shocks, local supersonic zones, turbulent zones.

Second. Due to the appearance of local supersonic zones on the wing profile and their further shift to the tail part of the profile with increasing flow speed and, thereby, changing the pressure distribution pattern on the profile, the point of application of aerodynamic forces (the center of pressure) also shifts to the trailing edge. As a result, it appears diving moment relative to the aircraft's center of mass, causing it to lower its nose.

What does all this result in... Due to a rather sharp increase in aerodynamic drag, the aircraft requires a noticeable engine power reserve to overcome the transonic zone and reach, so to speak, real supersonic sound.

A sharp increase in aerodynamic drag at transonics (wave crisis) due to an increase in wave drag. Сd - resistance coefficient.

Further. Due to the occurrence of a diving moment, difficulties arise in pitch control. In addition, due to the disorder and unevenness of the processes associated with the emergence of local supersonic zones with shock waves, control becomes difficult. For example, in roll, due to different processes on the left and right planes.

Moreover, there is the occurrence of vibrations, often quite strong due to local turbulence.

In general, a complete set of pleasures, which is called wave crisis. But, the truth is, they all take place (had, concrete :-)) when using typical subsonic aircraft (with a thick straight wing profile) in order to achieve supersonic speeds.

Initially, when there was not yet enough knowledge, and the processes of reaching supersonic were not comprehensively studied, this very set was considered almost fatally insurmountable and was called sound barrier(or supersonic barrier, if you want to:-)).

There have been many tragic incidents when trying to overcome the speed of sound on conventional piston aircraft. Strong vibration sometimes led to structural damage. The planes did not have enough power for the required acceleration. In horizontal flight it was impossible due to the effect, which has the same nature as wave crisis.

Therefore, a dive was used to accelerate. But it could well have been fatal. The diving moment that appeared during a wave crisis made the dive protracted, and sometimes there was no way out of it. After all, in order to restore control and eliminate the wave crisis, it was necessary to reduce the speed. But doing this in a dive is extremely difficult (if not impossible).

The pulling into a dive from horizontal flight is considered one of the main reasons for the disaster in the USSR on May 27, 1943 of the famous experimental fighter BI-1 with a liquid rocket engine. Tests were carried out for maximum flight speed, and according to the designers' estimates, the speed achieved was more than 800 km/h. After which there was a delay in the dive, from which the plane did not recover.

Experimental fighter BI-1.

In our time wave crisis is already quite well studied and overcoming sound barrier(if required :-)) is not difficult. On airplanes that are designed to fly at fairly high speeds, certain Constructive decisions and restrictions that facilitate their flight operation.

As is known, the wave crisis begins at M numbers close to one. Therefore, almost all subsonic jet airliners (passenger ones, in particular) have a flight limit on the number of M. Usually it is in the region of 0.8-0.9M. The pilot is instructed to monitor this. In addition, on many aircraft, when the limit level is reached, after which the flight speed must be reduced.

Almost all aircraft flying at speeds of at least 800 km/h and above have swept wing(at least along the leading edge :-)). It allows you to delay the start of the offensive wave crisis up to speeds corresponding to M=0.85-0.95.

Swept wing. Basic action.

The reason for this effect can be explained quite simply. On a straight wing, the air flow with a speed V approaches almost at a right angle, and on a swept wing (sweep angle χ) at a certain gliding angle β. Velocity V can be vectorially decomposed into two flows: Vτ and Vn.

The flow Vτ does not affect the pressure distribution on the wing, but the flow Vn does, which precisely determines the load-bearing properties of the wing. And it is obviously smaller in magnitude of the total flow V. Therefore, on a swept wing, the onset of a wave crisis and an increase wave resistance occurs significantly later than on a straight wing at the same free-stream speed.

Experimental fighter E-2A (predecessor of the MIG-21). Typical swept wing.

One of the modifications of the swept wing was the wing with supercritical profile(mentioned him). It also makes it possible to shift the onset of the wave crisis to higher speeds, and in addition, it makes it possible to increase efficiency, which is important for passenger airliners.

SuperJet 100. Swept wing with supercritical profile.

If the plane is intended for passage sound barrier(passing and wave crisis too :-)) and supersonic flight, it usually always differs in certain design features. In particular, it usually has thin wing profile and empennage with sharp edges(including diamond-shaped or triangular) and a certain form wing plan (for example, triangular or trapezoidal with overflow, etc.).

Supersonic MIG-21. Follower E-2A. A typical delta wing.

MIG-25. An example of a typical aircraft designed for supersonic flight. Thin wing and tail profiles, sharp edges. Trapezoidal wing. profile

Passing the proverbial sound barrier, that is, such aircraft make the transition to supersonic speed at afterburner operation of the engine due to the increase in aerodynamic resistance, and, of course, in order to quickly pass through the zone wave crisis. And the very moment of this transition is most often not felt in any way (I repeat :-)) either by the pilot (he may only experience a decrease in the sound pressure level in the cockpit), or by an outside observer, if, of course, he could observe it :-).

However, here it is worth mentioning one more misconception associated with outside observers. Surely many have seen photographs of this kind, the captions under which say that this is the moment the plane overcomes sound barrier, so to speak, visually.

Prandtl-Gloert effect. Does not involve breaking the sound barrier.

Firstly, we already know that there is no sound barrier as such, and the transition to supersonic itself is not accompanied by anything extraordinary (including a bang or an explosion).

Secondly. What we saw in the photo is the so-called Prandtl-Gloert effect. I have already written about him. It is in no way directly related to the transition to supersonic. It’s just that at high speeds (subsonic, by the way :-)), the plane, moving a certain mass of air in front of itself, creates a certain amount of air behind rarefaction region. Immediately after the flight, this area begins to fill with air from the nearby natural space. an increase in volume and a sharp drop in temperature.

If air humidity sufficient and the temperature drops below the dew point of the surrounding air, then moisture condensation from water vapor in the form of fog, which we see. As soon as conditions are restored to original levels, this fog immediately disappears. This whole process is quite short-lived.

This process at high transonic speeds can be facilitated by local shock waves I, sometimes helping to form something like a gentle cone around the plane.

High speeds favor this phenomenon, however, if the air humidity is sufficient, it can (and does) occur at fairly low speeds. For example, above the surface of reservoirs. Most, by the way, beautiful photos of this nature were made on board an aircraft carrier, that is, in fairly humid air.

This is how it works. The footage, of course, is cool, the spectacle is spectacular :-), but this is not at all what it is most often called. nothing to do with it at all (and supersonic barrier Same:-)). And this is good, I think, otherwise the observers who take this kind of photo and video might not be happy. Shock wave, do you know:-)…

In conclusion, there is one video (I have already used it before), the authors of which show the effect of a shock wave from an aircraft flying at low altitude at supersonic speed. There is, of course, a certain exaggeration there :-), but the general principle is clear. And again impressive :-)…

That's all for today. Thank you for reading the article to the end :-). Until next time...

Photos are clickable.

Illustration copyright SPL

Spectacular photographs of fighter jets in a dense cone of water vapor are often claimed to represent the aircraft breaking the sound barrier. But this is a mistake. The columnist talks about the true reason for the phenomenon.

This spectacular phenomenon has been repeatedly captured by photographers and videographers. A military jet plane passes over the ground on high speed, several hundred kilometers per hour.

As the fighter accelerates, a dense cone of condensation begins to form around it; it seems that the plane is inside a compact cloud.

The imaginative captions under such photographs often claim that this is visual evidence of a sonic boom when an aircraft reaches supersonic speed.

Actually this is not true. We are observing the so-called Prandtl-Glauert effect - a physical phenomenon that occurs when an aircraft approaches the speed of sound. It has nothing to do with breaking the sound barrier.

Other articles on the BBC Future website in Russian

As aircraft manufacturing developed, aerodynamic shapes became more and more streamlined, and the speed of aircraft steadily increased - aircraft began to do things with the air around them that their slower and bulkier predecessors were not capable of.

The mysterious shock waves that form around low-flying aircraft as they approach and then break the sound barrier suggest that air behaves in strange ways at such speeds.

So what are these mysterious clouds of condensation?

Illustration copyright Getty Image caption The Prandtl-Gloert effect is most pronounced when flying in a warm, humid atmosphere.

According to Rod Irwin, chairman of the aerodynamics group at the Royal Aeronautical Society, the conditions under which a cone of steam occurs immediately precede an aircraft breaking the sound barrier. However, this phenomenon is usually photographed at speeds slightly less than the speed of sound.

The surface layers of air are denser than the atmosphere at high altitudes. When flying at low altitudes, increased friction and drag occur.

By the way, pilots are prohibited from breaking the sound barrier over land. “You can go supersonic over the ocean, but not over a solid surface,” explains Irwin. “By the way, this circumstance was a problem for the supersonic passenger liner Concorde - the ban was introduced after it was put into operation, and the crew was allowed to develop supersonic speed only over water surface".

Moreover, it is extremely difficult to visually register a sonic boom when an aircraft reaches supersonic speed. It cannot be seen with the naked eye - only with the help of special equipment.

To photograph models blown at supersonic speeds in wind tunnels, special mirrors are usually used to detect the difference in light reflection caused by the formation of the shock wave.

Illustration copyright Getty Image caption When air pressure changes, the air temperature drops and the moisture it contains turns into condensation.

Photographs obtained by the so-called Schlieren method (or Toepler method) are used to visualize shock waves (or, as they are also called, shock waves) formed around the model.

During blowing, no cones of condensation are created around the models, since the air used in wind tunnels is pre-dried.

Cones of water vapor are associated with shock waves (of which there are several) that form around the aircraft as it gains speed.

When the speed of an aircraft approaches the speed of sound (about 1234 km/h at sea level), a difference in local pressure and temperature occurs in the air flowing around it.

As a result, the air loses its ability to retain moisture, and condensation forms in the shape of a cone, like on this video.

"The visible vapor cone is caused by a shock wave, which creates a difference in pressure and temperature in the air surrounding the aircraft," Irwin says.

Many of the best photographs of the phenomenon are from US Navy aircraft - not surprising, given that warm, moist air near the sea's surface tends to make the Prandtl-Glauert effect more pronounced.

Such stunts are often performed by F/A-18 Hornet fighter-bombers, the main type of carrier-based aircraft in American naval aviation.

Illustration copyright SPL Image caption The shock when an aircraft reaches supersonic speed is difficult to detect with the naked eye.

The same combat vehicles are used by members of the US Navy Blue Angels aerobatic team, who skillfully perform maneuvers in which a condensation cloud forms around the aircraft.

Because of the spectacular nature of the phenomenon, it is often used to popularize naval aviation. The pilots deliberately maneuver over the sea, where the conditions for the occurrence of the Prandtl-Gloert effect are most optimal, and professional naval photographers are on duty nearby - after all, it is impossible to take a clear picture of a jet aircraft flying at a speed of 960 km/h with a regular smartphone.

Condensation clouds look most impressive in the so-called transonic flight mode, when the air partially flows around the aircraft at supersonic speeds, and partially at subsonic speeds.

“The plane is not necessarily flying at supersonic speed, but the air flows over the upper surface of the wing at a higher speed than the lower surface, which leads to a local shock wave,” says Irwin.

According to him, for the Prandtl-Glauert effect to occur, certain climatic conditions are necessary (namely, warm and humid air), which carrier-based fighters encounter more often than other aircraft.

All you have to do is ask a professional photographer for the service, and voila! - your plane was captured surrounded by a spectacular cloud of water vapor, which many of us mistakenly take as a sign of reaching supersonic speed.

You can read it on the website

Sound barrier

a phenomenon that occurs during the flight of an aircraft or rocket at the moment of transition from subsonic to supersonic flight speed in the atmosphere. As the aircraft's speed approaches the speed of sound (1200 km/h), a thin region appears in the air in front of it, in which a sharp increase in pressure and density of the air occurs. This compaction of air in front of a flying aircraft is called a shock wave. On the ground, the passage of the shock wave is perceived as a bang, similar to the sound of a gunshot. Having exceeded , the plane passes through this area of increased air density, as if piercing it - breaking the sound barrier. For a long time breaking the sound barrier seemed to be a serious problem in the development of aviation. To solve it, it was necessary to change the profile and shape of the aircraft wing (it became thinner and swept-back), make the front part of the fuselage more pointed and equip the aircraft with jet engines. The speed of sound was first exceeded in 1947 by Charles Yeager on an X-1 aircraft (USA) with a liquid rocket engine launched from a B-29 aircraft. In Russia, O. V. Sokolovsky was the first to break the sound barrier in 1948 on an experimental La-176 aircraft with a turbojet engine.

Encyclopedia "Technology". - M.: Rosman. 2006 .

Sound barrier

a sharp increase in the drag of an aerodynamic aircraft at flight Mach numbers M(∞), slightly exceeding the critical number M*. The reason is that at numbers M(∞) > M* comes, accompanied by the appearance of wave resistance. The wave drag coefficient of aircraft increases very quickly with increasing number M, starting with M(∞) = M*.
Availability of Z. b. makes it difficult to achieve a flight speed equal to the speed of sound and the subsequent transition to supersonic flight. To do this, it turned out to be necessary to create aircraft with thin swept wings, which made it possible to significantly reduce drag, and jet engines, in which thrust increases with increasing speed.
In the USSR, a speed equal to the speed of sound was first achieved on the La-176 aircraft in 1948.

Aviation: Encyclopedia. - M.: Great Russian Encyclopedia. Chief Editor G.P. Svishchev. 1994 .

See what a “sound barrier” is in other dictionaries:

The sound barrier in aerodynamics is the name of a number of phenomena that accompany the movement of an aircraft (for example, a supersonic aircraft, a rocket) at speeds close to or exceeding the speed of sound. Contents 1 Shock wave, ... ... Wikipedia

SOUND BARRIER, the cause of difficulties in aviation when increasing flight speed above the speed of sound (SUPERSONIC SPEED). Approaching the speed of sound, the aircraft experiences an unexpected increase in drag and loss of aerodynamic lift... ... Scientific and technical encyclopedic dictionary

sound barrier- garso barjeras statusas T sritis fizika atitikmenys: engl. sonic barrier sound barrier vok. Schallbarriere, f; Schallmauer, f rus. sound barrier, m pranc. barriere sonique, f; frontière sonique, f; mur de son, m … Fizikos terminų žodynas

sound barrier- garso barjeras statusas T sritis Energetika apibrėžtis Staigus aerodinaminio pasipriešinimo padidėjimas, kai orlaivio greitis tampa garso greičiu (viršijama kritinė Macho skaičiaus vertė). Aiškinamas bangų krize dėl staiga padidėjusio… … Aiškinamasis šiluminės ir branduolinės technikos terminų žodynas

A sharp increase in aerodynamic drag as the aircraft's flight speed approaches the speed of sound (exceeding the critical value of the flight Mach number). Explained by a wave crisis, accompanied by an increase in wave resistance. Overcome 3.… … Big Encyclopedic Polytechnic Dictionary

Sound barrier- a sharp increase in air resistance to aircraft movement at. approaching speeds close to the speed of sound. Overcoming 3. b. became possible due to the improvement of the aerodynamic shapes of aircraft and the use of powerful... ... Glossary of military terms

sound barrier- sound barrier sharp increase in the resistance of an aerodynamic aircraft at flight Mach numbers M∞, slightly exceeding the critical number M*. The reason is that for numbers M∞ > Encyclopedia "Aviation"

- (French barriere outpost). 1) gates in fortresses. 2) in arenas and circuses there is a fence, a log, a pole over which a horse jumps. 3) the sign that the fighters reach in a duel. 4) railings, grating. Dictionary of foreign words included in... ... Dictionary of foreign words of the Russian language

BARRIER, ah, husband. 1. An obstacle (type of wall, crossbar) placed on the path (during jumping, running). Take b. (overcome it). 2. Fence, fencing. B. box, balcony. 3. transfer Obstruction, obstacle for what n. River natural b. For… … Dictionary Ozhegova