Who was the first to break the sound barrier? What happens when an airplane breaks the sound barrier The first object to break the speed of sound

Sometimes when a jet plane flies through the sky, you can hear a loud bang that sounds like an explosion. This "burst" is the result of the aircraft breaking the sound barrier.

What is the sound barrier and why do we hear an explosion? AND who was the first to break the sound barrier ? We will consider these questions below.

What is the sound barrier and how is it formed?

Aerodynamic sound barrier is a series of phenomena that accompany the movement of any aircraft(airplane, rocket, etc.), the speed of which is equal to or greater than the speed of sound. In other words, the aerodynamic “sound barrier” is a sharp jump in air resistance that occurs when an airplane reaches the speed of sound.

Sound waves travel through space at a certain speed, which varies depending on height, temperature and pressure. For example, at sea level the speed of sound is approximately 1220 km/h, at an altitude of 15 thousand m – up to 1000 km/h, etc. When the speed of an aircraft approaches the speed of sound, certain loads are applied to it. At normal speeds (subsonic), the nose of the aircraft “drives” a wave of compressed air in front of it, the speed of which corresponds to the speed of sound. The speed of the wave is greater than the normal speed of the aircraft. As a result, air flows freely around the entire surface of the aircraft.

But, if the speed of the aircraft corresponds to the speed of sound, the compression wave is formed not at the nose, but in front of the wing. As a result, a shock wave is formed, increasing the load on the wings.

In order for an aircraft to overcome the sound barrier, in addition to a certain speed, it must have a special design. That is why aircraft designers developed and used a special aerodynamic wing profile and other tricks in aircraft construction. At the moment of breaking the sound barrier, the pilot of a modern supersonic aircraft feels vibrations, “jumps” and “aerodynamic shock”, which on the ground we perceive as a pop or explosion.

Who was the first to break the sound barrier?

The question of the “pioneers” of the sound barrier is the same as the question of the first space explorers. To the question “ Who was the first to break the supersonic barrier? ? You can give different answers. This is the first person to break the sound barrier, and the first woman, and, oddly enough, the first device...

The first person to break the sound barrier was test pilot Charles Edward Yeager (Chuck Yeager). On October 14, 1947, his experimental Bell X-1 aircraft, equipped with a rocket engine, went into a shallow dive from an altitude of 21,379 m above Victorville (California, USA), and reached the speed of sound. The speed of the plane at that moment was 1207 km/h.

Throughout his career, the military pilot made a major contribution to the development of not only American military aviation, but also astronautics. Charles Elwood Yeager ended his career as a general in the US Air Force, having visited many parts of the world. The experience of a military pilot came in handy even in Hollywood when staging spectacular aerial stunts in the feature film “The Pilot.”

Chuck Yeager's story of breaking the sound barrier is told in the film "The Right Guys," which won four Oscars in 1984.

Other "conquerors" of the sound barrier

In addition to Charles Yeager, who was the first to break the sound barrier, there were other record holders.

The first Soviet test pilot - Sokolovsky (December 26, 1948).
The first woman is American Jacqueline Cochran (May 18, 1953). Flying over Edwards Air Force Base (California, USA), her F-86 aircraft broke the sound barrier at a speed of 1223 km/h.
The first civilian aircraft was the American passenger airliner Douglas DC-8 (August 21, 1961). Its flight, which took place at an altitude of about 12.5 thousand m, was experimental and was organized with the aim of collecting data necessary for the future design of the leading edges of the wings.
First car to break the sound barrier - Thrust SSC (October 15, 1997).
The first person to break the sound barrier in free fall was American Joe Kittinger (1960), who parachuted from a height of 31.5 km. However, after that, flying over the American city of Roswell (New Mexico, USA) on October 14, 2012, Austrian Felix Baumgartner set a world record by leaving balloon with a parachute at an altitude of 39 km. Its speed was about 1342.8 km/h, and its descent to the ground, most of which was in free fall, took only 10 minutes.
The world record for breaking the sound barrier by an aircraft belongs to the X-15 air-to-ground hypersonic aeroballistic missile (1967), currently in service Russian army. The rocket's speed at an altitude of 31.2 km was 6389 km/h. I would like to note that the maximum possible speed of human movement in the history of manned aircraft is 39,897 km/h, which was reached in 1969 by the American spaceship"Apollo 10".

The first invention to break the sound barrier

Oddly enough, the first invention that broke the sound barrier was... a simple whip, invented by the ancient Chinese 7 thousand years ago.

Before the invention of instant photography in 1927, no one would have thought that the crack of a whip was not just a strap hitting the handle, but a miniature supersonic click. During a sharp swing, a loop is formed, the speed of which increases several tens of times and is accompanied by a click. The loop breaks the sound barrier at a speed of about 1200 km/h.

Why does an airplane break the sound barrier with an explosive bang? And what is a “sound barrier”?

There is a misunderstanding with “pop” caused by a misunderstanding of the term “sound barrier.” This “pop” is properly called a “sonic boom.” Airplane moving from supersonic speed, creates shock waves and air pressure surges in the surrounding air. In a simplified way, these waves can be imagined as a cone accompanying the flight of an aircraft, with the apex, as it were, tied to the nose of the fuselage, and the generatrices directed against the movement of the aircraft and spreading quite far, for example, to the surface of the earth.

When the boundary of this imaginary cone, which marks the front of the main sound wave, reaches the human ear, a sharp jump in pressure is heard as a clap. The sonic boom, as if tethered, accompanies the entire flight of the aircraft, provided that the aircraft is moving fast enough, albeit at a constant speed. The clap seems to be the passage of the main wave of a sonic boom over a fixed point on the surface of the earth, where, for example, the listener is located.

In other words, if a supersonic plane began to fly back and forth over the listener at a constant but supersonic speed, then the bang would be heard every time, some time after the plane flew over the listener at a fairly close distance.

And the “sound barrier” in aerodynamics is a sharp jump in air resistance that occurs when an airplane reaches a certain boundary speed close to the speed of sound. When this speed is reached, the nature of the air flow around the aircraft changes dramatically, which at one time made it very difficult to achieve supersonic speeds. An ordinary, subsonic aircraft is not capable of flying steadily faster than sound, no matter how much it is accelerated - it will simply lose control and fall apart.

To overcome the sound barrier, scientists had to develop a wing with a special aerodynamic profile and come up with other tricks. It is interesting that the pilot of a modern supersonic aircraft has a good sense of “overcoming” the sound barrier with his aircraft: when switching to supersonic flow, an “aerodynamic shock” and characteristic “jumps” in controllability are felt. But these processes are not directly related to the “claps” on the ground.

Before the plane breaks the sound barrier, an unusual cloud may form, the origin of which is still unclear. According to the most popular hypothesis, a drop in pressure occurs near the aircraft and a so-called Prandtl-Glauert singularity followed by condensation of water droplets from moist air. Actually, you see the condensation in the photos below...

Click on the picture to enlarge it.

An unusual picture can sometimes be observed during the flight of jet aircraft, which seem to emerge from a cloud of fog. This phenomenon is called the Prandtl-Gloert effect and consists of the appearance of a cloud behind an object moving at transonic speed in conditions of high air humidity.

The reason for this unusual phenomenon is that the person flying high speed An airplane creates an area of high air pressure in front of itself and an area of low pressure behind it. After the plane passes, the area of low pressure begins to fill with ambient air. In this case, due to the sufficiently high inertia of air masses, first the entire low pressure area is filled with air from nearby areas adjacent to the low pressure area.

This process is locally an adiabatic process, where the volume occupied by the air increases and its temperature decreases. If the air humidity is high enough, the temperature can drop to such a value that it is below the dew point. Then the water vapor contained in the air condenses into tiny droplets, which form a small cloud.

Clickable 2600 px

As the air pressure normalizes, the temperature in it evens out and again rises above the dew point, and the cloud quickly dissolves into the air. Usually its lifetime does not exceed a fraction of a second. Therefore, when an airplane flies, the cloud appears to follow it - due to the fact that it constantly forms immediately behind the airplane and then disappears.

There is a common misconception that the appearance of a cloud due to the Prandtl-Glauert effect means that this is the moment the aircraft breaks the sound barrier. Under conditions of normal or slightly increased humidity, a cloud forms only at high speeds, close to the speed of sound. At the same time, when flying at low altitude and in conditions of very high humidity (for example, over the ocean), this effect can be observed at speeds significantly lower than the speed of sound.

Clickable 2100 px

There is a misunderstanding with “clap” caused by a misunderstanding of the term “sound barrier.” This “pop” is correctly called a “sonic boom.” An airplane moving at supersonic speed creates shock waves and air pressure surges in the surrounding air. In a simplified way, these waves can be imagined as a cone accompanying the flight of an aircraft, with the apex, as it were, tied to the nose of the fuselage, and the generatrices directed against the movement of the aircraft and spreading quite far, for example, to the surface of the earth.

Clickable 2500 px

But look at what an interesting shot! This is the first time I've seen this!

Clickable 1920 px - to whom on the table!

What do we imagine when we hear the expression “sound barrier”? A certain limit can seriously affect hearing and well-being. The sound barrier is usually associated with conquering 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? We will try to find out all this and some additional nuances, as well as historical facts related to 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 the 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. Plenty of transport, hundreds of restaurants and entertainment centers confuse and unsettle you from your usual rut. 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 roar of cars on particularly busy highways exceeds all permissible standards twice as much. 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. This is why good health and emotional stability are so important for pilots. 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 looked like a modern one cruise missile with 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 the technical parameters of 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 went to the Air Force units, where he trained pilots. The last time Chuck Yeager broke the sound barrier was 74 years old, which was on 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 complex problems had to be solved. technical problems. As a result, a machine was created so successful that its modifications entered service different countries. Several different design bureaus got involved in a kind of competition, the prize of 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.

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 aircraft, if it flies at high altitude, may 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 quite complex system shock waves. 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 ample evidence of this (especially in history 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 if certain piloting rules are observed, it 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 a 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.

To form numerous shock waves (or shock waves) during deceleration of a supersonic flow, as I said above, energy is wasted, and it is taken from the kinetic energy of the aircraft’s motion. 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.

Profile swelling at different Mach numbers. Shock 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 dive 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 on maximum speed flight, 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 :-)) special labor does not make up. On airplanes that are designed to fly at fairly high speeds, certain design solutions and restrictions are applied to 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 wing shape in 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 it 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 general principle understandable. And again impressive :-)…

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

Photos are clickable.

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