What happens when you overcome the speed of sound. Sound barrier. Verbal and material monuments to the conquest of the speed of sound

Passed the sound barrier: -) ...

Before we start talking on the topic, let's make some clarity about the accuracy of the concepts (what I like :-)). Now two terms are in fairly wide use: sound barrier and supersonic barrier... They sound similar, but not the same. However, it makes no sense to breed a special rigor: in fact, they are one and the same. The definition of a 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. Here's a simple logic. After all, there is the concept of the speed of sound, but, strictly speaking, there is no fixed concept of the speed of supersonic. Running a little ahead of myself, I will say that when an aircraft flies in supersonic, it has already passed this barrier, and when it passes it (overcomes), it passes a certain threshold speed value equal to the speed of sound (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 a supersonic flight, exotic is certainly present and, naturally, attracts many. However, not all people savoring the words “ supersonic barrier"They really understand what it is. More than once I was convinced of this, looking at the forums, reading articles, even watching TV.

This question is actually quite complicated from the point of view of physics. But we, of course, will not climb in complexity. Let's just try, as usual, to clarify the situation using the principle of "explaining aerodynamics on the fingers" :-).

So, to the (sound :-)) barrier! ... 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 the air are :-).

Sound waves (tuning fork).

This is an alternation of areas of compression and rarefaction, spreading in different directions from the sound source. Roughly like circles on the water, which are also just waves (but 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 parts of the aircraft. For example, an engine (its sound is known to anyone :-)), or body parts (for example, the nose), which, by compressing air in front of them when moving, create a certain type of pressure (compression) waves running forward.

All these sound waves propagate in air at the speed of sound we already know. 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 flies by itself.

I'll 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 in which the sound appears for the listener and the plane, if it flies at 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 emitted by it. That is, if he were stationary, then the waves would diverge from him in the form concentric circleslike circles on water from 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.

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 there is a gradual, to a certain extent, deceleration oncoming flow when meeting with the nose of the aircraft (wing, tail unit) and, as a result, increase in pressure and temperature) begins to decrease 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 region, which is called shock wave... This happens when the flight speed reaches the speed of sound, that is, the plane is moving at the same speed as the waves emitted by it. In this case, the Mach number is equal to one (M \u003d 1).

Sound movement of the body (M \u003d 1).

Compaction 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 (abrupt) change in the parameters of this medium - speed, pressure, temperature, density... In our case, the speed decreases, the pressure, temperature and density increase. Hence the name - shock wave.

In a somewhat simplified way, I would also say so about all this. It is impossible to decelerate the supersonic flow sharply, but it has to do it, because there is no longer the possibility of gradual deceleration to the flow velocity in front of the very nose of the aircraft, as at moderate subsonic speeds. It kind of stumbles upon the subsonic section in front of the aircraft's nose (or the toe of a wing) and crumples into a narrow jump, transferring to it the great energy of motion that it possesses.

By the way, it can be said, and vice versa, that 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 is, in fact, a front of a sharp change in the above parameters of the environment (that is, air flow). And this is the essence of the shock wave.

Compaction shock and a shock wave, in general, are equal definitions, but in aerodynamics the first is more used.

The shock wave (or shock wave) can be practically perpendicular to the direction of flight, in this case they take in space approximately the shape of a circle and are called straight lines. This usually happens in modes close to M \u003d 1.

Modes of body movement. ! - subsonic, 2 - M \u003d 1, supersonic, 4 - shock wave (shock wave).

At numbers M\u003e 1, they are already located at an angle to the direction of flight. That is, the plane is already overtaking 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, after the name of a scientist who studied supersonic flows (he mentioned it in one of the).

Mach cone.

The shape of this cone (its so-called "harmony") just depends on the number M and is related to it by the ratio: M \u003d 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 aircraft, and which it "overtook", reaching supersonic speed.

Besides shock waves may also attachedwhen they adjoin the surface of a body moving at supersonic speed, or when they have moved away, if they are not in contact with the body.

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

The jumps usually become attached if the supersonic flow flows around any sharp-pointed surfaces. For an aircraft, for example, this can be a pointed nose, LDPE, or a sharp edge of the air intake. At the same time, they say "the jump sits", for example, on the nose.

A retreating jump can be obtained when flowing around rounded surfaces, for example, the front rounded edge of a thick wing airfoil.

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 head on the bow and the second on the tail on the elements of the tail. At some distance from the aircraft, intermediate jumps either catch up with the head one and merge with it, or the tail jumps overtake them.

Seal jumps on a model airplane during blowing in a wind tunnel (M \u003d 2).

As a result, there are two jumps, which, in general, are perceived by the terrestrial observer as one because of the small size of the aircraft compared to the flight altitude and, accordingly, the small time interval between them.

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

As the distance from the top of the Mach cone, that is, from the aircraft, as a source of disturbances, the shock wave weakens, gradually turns into an ordinary sound wave, and eventually completely disappears.

And from what degree of intensity will have shock wave (or shock wave) that reaches the ground depends on the effect that it can produce there. It's no secret that the well-known "Concorde" flew supersonic only over the Atlantic, and military supersonic aircraft go to supersonic 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 glass from windows can come out easily. 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. One has only to fly lower :-) ...

However, for the most part, what remains from the 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 crash or explosion. It is with this fact that one common and rather persistent misconception is associated.

People who are not too sophisticated in aviation science, hearing such a sound, say that this plane overcame sound barrier (supersonic barrier). In fact, this is not the case. 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 resounding rumble high in the sky, then this only means (I repeat :-)) that he has reached his ears shock front (or shock wave) from an airplane flying somewhere. This plane is already flying at supersonic speed, and not just switched to it.

And if the same person could suddenly be several kilometers ahead of the plane, then he would again hear the same sound from the same plane, because he would have been hit by the same shock wave moving along 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 (well, when only on them :-)) and safely goes on, the hum of the working engines becomes audible.

Approximate flight pattern of the aircraft at various values \u200b\u200bof the M 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 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 by reading the instruments. In this case, however, a certain process occurs, but it is practically invisible to him if certain piloting rules are observed.

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

Strictly speaking, there is no barrier at all. Sometime at the dawn of mastering high speeds in aviation, this concept was formed rather as a psychological conviction about the difficulty of switching to supersonic speed and flying at it. There were even statements that this was generally impossible, especially since the preconditions 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 an air flow of a body moving in this flow and striving to go to supersonic. it wave crisis... It is he who does some of the 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 in flight may not be the same. Take, for example, a wing, or rather an ordinary classic subsonic profile.

From the basics of knowledge about how lift We know well that the flow rate 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 total flow velocity, then, when the profile flattens, it decreases.

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

Local shock wave appearing on transonic 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 decelerate, therefore, the occurrence of shock wave.

Such jumps appear in different parts of the streamlined surfaces, and initially they are rather weak, but their number can be large, and with an increase in the total flow velocity, the supersonic zones increase, the jumps "get stronger" and shift to the trailing edge of the airfoil. Later, the same shock waves appear on the lower surface of the profile.

Full supersonic flow around the wing profile.

What is all this fraught with? And here's what. The firstIs significant increase in aerodynamic drag in the range of transonic speeds (about M \u003d 1, more or less). This resistance grows due to a sharp increase in one of its components - wave resistance... The one 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 spent, and it is taken from the kinetic energy of the motion of the aircraft. That is, the plane is simply slowed down (and very noticeably!). That's what it is wave resistance.

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

Profile swelling at different M numbers. Compaction jumps, local supersonic zones, turbulent zones.

Second... Due to the appearance of local supersonic zones on the wing airfoil and their further shift to the tail of the airfoil with an increase in the flow velocity and, thereby, a change in the pressure distribution pattern on the airfoil, the point of application of aerodynamic forces (center of pressure) also shifts to the trailing edge. The result is dive moment relative to the center of mass of the aircraft, causing it to lower its nose.

What does all this translate into ... Due to the rather sharp increase in aerodynamic drag, the aircraft requires a significant engine power reserve to overcome the trance zone and enter, so to speak, real supersonic.

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

Further. Due to the appearance of the diving moment, there are difficulties 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, too difficult to manage... For example, by roll, due to different processes on the left and right planes.

Plus the occurrence of vibrations, often quite strong due to local turbulence.

In general, a complete set of pleasures that bears the name wave crisis... But, it is true, they all take place (had, specific :-)) when using typical subsonic aircraft (with a thick straight wing profile) in order to achieve supersonic speeds.

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

When trying to overcome the speed of sound on conventional piston aircraft, there were many tragic cases. Strong vibration sometimes led to structural damage. The aircraft did not have enough power for the required acceleration. In level flight, it was impossible due to an effect of the same nature as wave crisis.

Therefore, a dive was used for overclocking. But it could very well be fatal. The diving moment appearing during a wave crisis made the peak protracted, and sometimes there was no way out of it. Indeed, to restore control and eliminate the wave crisis, it was necessary to extinguish the speed. But doing it in a dive is extremely difficult (if not impossible).

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

Experimental fighter BI-1.

Nowadays wave crisis already well studied and overcoming sound barrier (if required :-)) is not difficult. On airplanes that are designed to fly at high enough speeds, certain design solutions and restrictions are applied to facilitate their flight operation.

As you know, a wave crisis begins when M numbers are close to unity. Therefore, almost all jet subsonic liners (passenger, in particular) have a flight restriction 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 postpone the start of the offensive wave crisis to speeds corresponding to M \u003d 0.85-0.95.

Swept wing. Principal action.

The reason for this effect can be explained quite simply. On a straight wing, the air flow at a speed V runs almost at a right angle, and on a swept wing (sweep angle χ) at a certain slip angle β. Velocity V can be decomposed into two streams in vector terms: Vτ and Vn.

The Vτ flux does not affect the pressure distribution on the wing, but it does the Vn flux, which determines the wing bearing properties. And it is obviously less in terms of the value of the total flow V. Therefore, on the swept wing, the onset of a wave crisis and growth wave resistance occurs noticeably later than on a straight wing at the same incoming flow velocity.

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

One of the modifications of the swept wing was a wing with supercritical profile (mentioned him). It also allows you to shift the beginning of the wave crisis at high speeds, in addition, it allows you to increase efficiency, which is important for passenger liners.

SuperJet 100. Supercritical swept wing.

If the plane is intended to go sound barrier (passing and wave crisis also :-)) and supersonic flight, then it usually always differs in certain design features... In particular, it usually has thin wing and tail profile with sharp edges (including diamond or triangular) and a certain wing shape in plan (for example, triangular or trapezoidal with a sag, etc.).

Supersonic MIG-21. Emissary E-2A. A typical triangular wing.

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

Passage of the notorious sound barrier, that is, the transition to supersonic speed such aircraft are carried out at engine afterburner due to the increase in aerodynamic drag, and, of course, in order to quickly pass the zone wave crisis... And the very moment of this transition is most often not felt in any way (I repeat :-)) neither by the pilot (except that the sound pressure level in the cockpit may decrease), nor by an outside observer, if, of course, he could observe this :-).

However, here it is worth mentioning another delusion associated with outside observers. Surely many have seen this kind of photos, the captions under which say that this is the moment of overcoming the plane sound barrier, so to speak, visually.

The Prandtl-Gloert effect. Not associated with passing the sound barrier.

First of all, we already know that there is no sound barrier, as such, and the transition to supersonic itself is not accompanied by anything so extraordinary (including a pop or explosion).

Secondly... What we saw in the photo is the so-called prandtl-Gloert effect... I already wrote about it. It is in no way directly related to the transition to supersonic. Just at high speeds (subsonic, by the way :-)) the plane, moving a certain mass of air in front of it, creates some rarefaction area... Immediately after the flight, this area begins to fill with air from a nearby space with natural an increase in volume and a sharp drop in temperature.

If a air humidityis sufficient and the temperature drops below the dew point of the ambient air, then moisture condensationfrom water vapor in the form of fog, which we see. As soon as conditions are restored to their original conditions, this fog immediately disappears. This whole process is rather short-lived.

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

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

And so it turns out. The shots, of course, are cool, the spectacle is spectacular :-), but this is not at all what it is most often called. it has nothing to do with it (and supersonic barrier also:-)). 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, 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 with supersonic speed. There is, of course, a certain exaggeration there :-), but the general principle is clear. And again, spectacular :-) ...

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

Photos are clickable.

On October 14, 1947, humanity crossed the next milestone. The boundary is quite objective, expressed in a specific physical quantity - the speed of sound in air, which in the conditions of the earth's atmosphere depends on its temperature and pressure in the range of 1100-1200 km / h. American pilot Charles Elwood "Chuck" Yeager, a young WWII veteran with extraordinary courage and excellent photogenicity, conquered supersonic speed, thanks to which he immediately became popular in his homeland, just as Yuri Gagarin was 14 years later.

And the courage to cross the sound barrier was really required. The Soviet pilot Ivan Fedorov, who repeated Yeager's achievement a year later, in 1948, recalled his feelings at that time: “Before the flight to overcome the sound barrier, it became obvious that there was no guarantee to survive after it. Nobody knew in practice what it was and whether the structure of the aircraft would withstand the pressure of the elements. But they 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 an 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 cars fell apart in the air. For quite a long time, mathematicians and designers 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 understandable 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 had to rely on "blowing" the models in wind tunnels. But from qualitative considerations it was clear that when the speed of sound is reached, a shock wave arises 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 opposite sides of the wave front increases rapidly, and if the moment lasts longer than a moment, the plane can collapse no worse than from a flutter. Sometimes, when overcoming the sound barrier with insufficient acceleration, the shock wave created by the aircraft even knocks glass from the windows of houses on the ground below it.

The ratio of the speed of an airplane to the speed of sound is called the Mach number (after the famous German mechanic and philosopher Ernst Mach). When passing the sound barrier, it seems to the pilot that the number M jumps over the unit in a jump: Chuck Yeager saw the mahometer needle jump from 0.98 to 1.02, after which a "divine" silence fell in the cockpit - in fact, it seemed: just a level the sound pressure in the cockpit drops several times. This moment of "sound purification" is very insidious, it cost the lives of many testers. But the danger of falling apart for his X-1 plane was small.

The X-1, manufactured by Bell Aircraft in January 1946, was purely a research aircraft designed to break the sound barrier and nothing else. Despite the fact that the machine was ordered by the Ministry of Defense, instead of weapons, it was stuffed with scientific equipment that monitors the modes of operation of units, devices 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 takeoff weight - 6078 kg. Length - 9.45 m, height - 3.3 m, wingspan - 8.53 m.Maximum speed - 2736 km / h at an altitude of 18290 m. The car started from strategic bomber B-29, 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 he went to a flight school, and after graduation he went to fight in Europe. Shot down one Messerschmitt-109. He himself was shot down in the skies of France, but he was saved by partisans. As if nothing had happened, he returned to the base in England. However, the vigilant counterintelligence service, not believing the miraculous deliverance from captivity, removed the pilot from flights and sent him to the rear. The ambitious Yeager got a reception from 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 until the end of the war, the young pilot made 64 sorties, 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 indicated that he possesses phenomenal flying intuition, incredible composure and amazing endurance in any critical situation. Thanks to such a characteristic, he was included in the team of supersonic testers, who were selected and trained as carefully as the astronauts later.

Renaming the X-1 Glamorous Glennis after his wife, Yeager has set records on it more than once. At the end of October 1947, the previous altitude record fell - 21,372 m. In December 1953, a new modification of the machine - the X-1A developed a speed of 2.35 M - almost 2800 km / h, and six months later it rose to a height of 27,430 m. That was the tests of a number of fighters that were launched into series and the running-in of our MiG-15, captured and transported to America during the Korean War. Subsequently, Yeager commanded various test units of the Air Force both in the United States and at American bases in Europe and Asia, took part in hostilities 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, running 180 different supersonic models and collecting a unique collection of orders and medals. In the mid-80s, a film was shot based on the biography of a gallant 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 nationwide relic. He last sat in the F-16 on October 14, 1997 and broke the sound barrier on the fiftieth anniversary of his historic flight. Yeager was then 74 years old. In general, as the poet said, nails would be made of these people.

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

Several design bureaus joined the competition - the Lavochkin Design Bureau, the Mikoyan Design Bureau and the Yakovlev Design Bureau - in which swept-wing aircraft were developed in parallel, which was then a revolutionary design decision. They came to 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, minimum pre-flight preparation time, powerful weapons, impressive ammunition, etc. etc. It should also be noted that in Soviet times, the decision of state acceptance commissions was often influenced not only by objective factors, but also by subjective factors associated with the political maneuvers of developers. All this combination of circumstances led to the fact that the MiG-15 fighter was launched into the series, which showed itself perfectly on the local arenas of military operations of the 50s. It was this car, seized in Korea, as mentioned above, that Chuck Yeager “drove around”.

In La-176, a record sweep of the wing for those times was used, 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. Takeoff weight - 4636 kg. The ceiling is 15,000 m. The flight range is 1,000 km. Armament - one 37-mm cannon and two 23-mm. The vehicle was ready in the fall of 1948, and in December its flight tests began in the Crimea at a military airfield near the city of Saki. Among those who led the tests was the future academician Vladimir Vasilievich 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, forgetting to close the cockpit canopy.

Colonel Ivan Fyodorov broke the sound barrier on December 26, 1948. Having risen to a height of 10 thousand meters, he pushed the control stick away from him and began to accelerate in a dive. “I accelerate my 176th from a great height,” the pilot recalled. - A tedious low whistle is heard. Increasing speed, the plane rushes to the ground. On the scale of the tachymeter, the arrow changes from three-digit numbers to four-digit ones. The plane trembles as if in a fever. And suddenly - silence! The sound barrier is taken. The subsequent decoding of the oscillograms showed that the number M exceeded one. " It happened at an altitude of 7,000 meters, where a speed of 1.02M was recorded.

In the future, the speed of manned aircraft continued to steadily increase due to the increase in engine power, the use of new materials and optimization of aerodynamic parameters. However, this process is not limitless. On the one hand, it is hampered 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 the safety of the pilot are not so important, the speeds of the most "nimble" machines are in the range from 1.5M to 3M. More as if not required. (Speed \u200b\u200brecord for manned vehicles with jet engines belongs to the American reconnaissance aircraft SR-71 and is 3.2M.)

On the other hand, there is an insurmountable thermal barrier: at a certain speed, the heating of the machine body by friction against 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 about 10M.

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

In accordance with the program, three unmanned models were manufactured, which, after completing the assignment, 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 for the needs of NASA, hypersonic military vehicles will be created - bombers, reconnaissance aircraft and transport aircraft. Boeing, which participates in the Hiper-X program, plans to create a 250-passenger hypersonic airliner by 2030-2040. It is quite understandable that there will be no windows that break aerodynamics at such speeds and cannot withstand thermal heating. Instead of portholes, screens with video recording of passing clouds are supposed.

There is no doubt that this type of transport will be in demand, since the further, the more expensive the time is, containing more and more emotions, dollars and other components earned per unit of time. modern life... In this regard, there is no doubt that someday people will turn into one-day butterflies: one day will be as rich as the whole current (rather, yesterday's) human life. And we can assume that someone or something is implementing the Hiper-X program in relation to humanity.

Sometimes, when a jet is flying in the sky, you can hear a loud bang, which sounds like an explosion. This "burst" is the result of the aircraft breaking the sound barrier.

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

What is a sound barrier and how is it formed?

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

Sound waves travel through space at a specific speed that changes with altitude, temperature, and pressure. For example, at sea level the speed of sound is about 1220 km / h, at an altitude of 15 thousand meters - 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 (subsonic) speeds, 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 wave speed is greater than the normal airplane speed. 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 on the nose, but in front of the wing. As a result, a shock wave is formed, which increases the load on the wings.

For the aircraft to be able to overcome the sound barrier, in addition to a certain speed, it must have a special design. That is why aircraft designers have developed and applied 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 impact", which we perceive on the ground 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 conquerors of space. To the question “ Who was the first to overcome the supersonic barrier ? " different answers can be given. This is the first person to break the sound barrier, and the first woman, and, oddly enough, the first device ...

The first to break the sound barrier was test pilot Charles Edwurd Yeager (Chuck Yeager). On October 14, 1947, his experimental aircraft Bell X-1, equipped with a rocket engine, went into a gentle dive from a height of 21379 m above Victorville (California, USA) and reached the speed of sound. The speed of the aircraft at this moment was 1207 km / h.

Throughout his career, the military pilot made a great contribution to the development of not only American military aviation, but also astronautics. Charles Elwood Yeager ended his career as an Air Force General, having traveled to 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 "Pilot".

Chuck Yeager's story of breaking the sound barrier is told by the film Guys That Needed, 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.

1. The first Soviet test pilot - Sokolovsky (December 26, 1948).
2. The first woman is American Jacqueline Cochran (May 18, 1953). Flying over Edwards Air Force Base (California, USA), her F-86 broke the sound barrier at a speed of 1223 km / h.
3. The first civil 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 meters, was experimental and organized to collect data necessary for the future design of the leading edges of the wings.
4. The first car to break the sound barrier - Thrust SSC (October 15, 1997).
5. The first person to break the sound barrier in free fall was American Joe Kittinger (1960), who jumped with a parachute from a height of 31.5 km. However, after him, flying over the American city of Roswell (New Mexico, USA) on October 14, 2012, Austrian Felix Baumgartner set a world record, leaving balloon with a parachute at an altitude of 39 km. At the same time, its speed was about 1342.8 km / h, and the descent to the ground, most of which was in free fall, took only 10 minutes.
6. The world record for breaking the sound barrier by an aircraft belongs to the X-15 hypersonic aeroballistic missile of the air-to-ground class (1967), which is now in service with the Russian army. The rocket 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 39897 km / h, which was reached in 1969 by the American spaceship Apollo 10.

First invention to break the sound barrier

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

Until the invention of instant photography in 1927, no one would have thought that the snap of the whip was not just the bang of the strap on the handle, but a miniature supersonic snap. 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.

What do we imagine when we hear the expression "sound barrier"? A certain limit and which can seriously affect hearing and well-being. Usually the sound barrier is related to the conquest of airspace and

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

This mysterious science is aerodynamics

In the science of aerodynamics, designed to explain the phenomena that accompany motion
aircraft, there is the concept of "sound barrier". This is a series of phenomena that occur when supersonic aircraft or rockets move at speeds close to the speed of sound or greater.

What is a shock wave?

In the process of supersonic flow around the vehicle, a shock wave arises in a wind tunnel. Its traces can be seen even with the naked eye. On the ground, they are shown with a yellow line. Outside the cone of the shock wave, in front of the yellow line, on the ground, the plane is not even heard. At a speed exceeding the sound speed, the bodies are subjected to a flow of sound, which entails a shock wave. She may not be alone, depending on the shape of the body.

Shock wave transformation

The shock front, which is sometimes called a shock wave, has a rather small thickness, which nevertheless makes it possible to track abrupt changes in the properties of the flow, a decrease in its velocity 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 the internal energy of the gas. The amount of these changes directly depends on the speed of the supersonic flow. As the shock wave moves away from the vehicle, pressure drops decrease and the shock wave is converted into sound. She can reach an outside observer who hears a characteristic sound that resembles an explosion. There is an opinion that this indicates that the vehicle 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 is the passage of a shock wave with a growing rumble of aircraft engines. Now the apparatus is ahead of the accompanying sound, so the hum of the engine will be heard after it. Approaching the speed to the speed of sound became possible during the Second World War, but at the same time, the pilots noted alarming signals in the operation of the aircraft.

After the end of the war, many aircraft designers and pilots sought to achieve the speed of sound and overcome 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 when avoiding a wave crisis, the occurrence of which depends on the aerodynamic parameters of the aircraft and the altitude of the flight being performed. Transitions from one speed level to another should be performed as quickly as possible with the use of afterburner, which will help to avoid a long flight in the wave crisis zone. Wave crisis as a concept came from water transport. It arose when ships were moving at a speed close to the speed of waves on the surface of the water. Getting into a wave crisis entails a difficulty in increasing the speed, and if it is as easy as possible to overcome the wave crisis, then you can enter the planing or sliding mode on the water surface.

History in aircraft control

The first person to reach supersonic flight speed in an experimental aircraft is the American pilot Chuck Yeager. His achievement is 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.

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

50 years after breaking the sound barrier in the air, Englishman Andy Green made a similar achievement in a car. In free fall, the American Joe Kittinger tried to break the record, who conquered a height of 31.5 kilometers. Today, on October 14, 2012, Felix Baumgartner set a world record, without the aid of transport, in free fall from a height of 39 kilometers, breaking the sound barrier. At the same time, its speed reached 1342.8 kilometers per hour.

The most unusual sound barrier breaking

It’s strange to think, but the first invention in the world to overcome this limit was an 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 flick of a whip was a miniature sonic boom. A sharp swing forms a loop, and the speed increases sharply, which is confirmed by a click. The sound barrier is overcome at a speed of about 1200 km / h.

The Noisiest City Mystery

It is not for nothing that residents of small towns are shocked when they see the capital for the first time. An abundance of transport, hundreds of restaurants and entertainment centers confused and unsettled. The beginning of spring in the capital is usually dated April, and not a rebellious blizzard March. In April there is a clear sky, streams run and buds bloom. People tired of the long winter open their windows wide to the sun, and street noise bursts into their houses. On the street, birds chirp deafeningly, artists sing, funny students recite poetry, not to mention the noise in traffic jams and the subway. Employees of the hygiene departments note that being in a noisy city for a long time is unhealthy. The sound background of the capital consists of transport,
aviation, industrial and domestic noise. The most harmful is just car noise, since airplanes fly high enough, and the noise from enterprises dissolves in their buildings. The constant hum of cars on especially busy highways doubles all permissible standards. How is the sound barrier overcome in the capital? Moscow is dangerous with an abundance of sounds, so residents of the capital install double-glazed windows to muffle the noise.

How is the storming of the sound barrier carried out?

Until 1947, there was no actual data on the health of a person in the cockpit of an aircraft that flies faster than sound. As it turned out, breaking the sound barrier requires a certain amount of strength and courage. During the flight, it becomes clear that there are no guarantees of survival. Even a professional pilot cannot say for sure whether the structure of an aircraft will withstand an attack of the elements. In a matter of minutes, the plane can simply fall apart. What explains this? It should be noted that movement with subsonic speed creates acoustic waves that scatter like circles from a falling stone. Supersonic speed excites shock waves, and a person standing on the ground hears a sound like an explosion. Without powerful computers, it was difficult to solve complex ones and had to rely on blowing models in wind tunnels. Sometimes, with insufficient acceleration of the aircraft, the shock wave reaches such a force that windows fly out of the houses over which the aircraft flies. Not everyone will be able to overcome the sound barrier, because at this moment the entire structure is shaking, the apparatus mounts can receive significant damage. This is why good health and emotional stability are so important to pilots. If the flight is smooth, and the sound barrier is overcome as quickly as possible, then neither the pilot nor potential passengers will feel particularly unpleasant sensations. A research aircraft was built specifically to conquer 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 devices. This plane was like a modern cruise missile with an integrated rocket engine. The aircraft crossed the sound barrier at a maximum speed of 2736 km / h.

Verbal and material monuments to the conquest of the speed of sound

Advances in breaking the sound barrier are still highly regarded today. So, the plane on which Chuck Yeager first overcame it, is now on display at the National Museum of Aeronautics and Astronautics, 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. Unjust suspension from flights did not break the spirit of Yeager, and he achieved a reception from the commander-in-chief of the troops of Europe. During the years remaining until the end of the war, Yeager participated in 64 sorties, 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. On more than one occasion, Yeager has set records on his plane. His further career was in the Air Force, where he carried out pilot training. The last time Chuck Yeager broke the sound barrier was 74 years old, which fell on the fiftieth anniversary of his flying history and in 1997.

Complex tasks of aircraft designers

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 overcoming the sound barrier, but complex technical problems had to be solved. As a result, a machine was created so successful that its modifications were adopted by different countries. Several different design bureaus were involved in a kind of competitive struggle, the prize of which was a patent for the most successful and functional aircraft. Swept-wing aircraft were developed, which was a revolution in their design. The ideal machine would be powerful, fast, and incredibly resistant to any external damage. The swept wings of the aircraft became an element that helped them triple the speed of sound. Then it continued to grow, which was explained by the increase in engine power, the use of innovative materials and the optimization of aerodynamic parameters. Overcoming the sound barrier has become possible and real even for a non-professional, but it does not become less dangerous because of this, so any extreme should sensibly assess their strengths before deciding on such an experiment.

Image copyright SPL

ABOUT impressive photos jet fighters in a dense cone of water vapor are often said to be a plane breaking the sound barrier. But this is a mistake. The observer talks about the true reason for the phenomenon.

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

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

The captions that haunt the imagination under such photographs often claim that we are faced with visual evidence of a sonic boom when an aircraft reaches supersonic speed.

In fact this is not true. We observe the so-called Prandtl-Glauert effect - a physical phenomenon that occurs when an aircraft approaches the speed of sound. It is not associated with breaking the sound barrier.

• Other BBC Future articles in Russian

With the development of aircraft construction, aerodynamic shapes became more streamlined, and the speed of aircraft grew steadily - aircraft began to do things with the air around them that their slower and more cumbersome predecessors were not capable of.

The mysterious shock waves that form around low-flying aircraft as they approach the speed of sound and then break the sound barrier indicate that air at such speeds behaves in a very strange way.

So what are these mysterious clouds of condensation?

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

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

Surface air layers are denser than the atmosphere at high altitudes. When flying at low altitudes, there is increased friction and drag.

By the way, pilots are prohibited from crossing the sound barrier over land. “You can go to 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 its commissioning, 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 sound. You cannot see it with the naked eye - only with the help of special equipment.

For photographs of 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 a shock wave.

Image copyright Getty Image caption With a drop in air pressure, the temperature of the air decreases and the moisture contained in it turns into condensate

Photographs obtained by the so-called schlieren method (or Tepler's method) are used to visualize shock waves (or, as they are also called, shock waves) generated around the model.

Condensation cones are not created around the models during blowing, since the air used in the wind tunnels is pre-dried.

Water vapor cones are associated with shock waves (and there are several of them) that form around the aircraft as it gains speed.

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

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

"The visible cone of vapor is caused by a shock wave, which creates a pressure and temperature drop in the air around the plane," says Irwin.

Many of the most successful photographs of the phenomenon have captured US Navy aircraft - not surprising, given that warm, humid air near the sea's surface tends to contribute to a more pronounced Prandtl-Glauert effect.

Such tricks are often performed by the F / A-18 Hornet fighter-bombers - the main type of deck-based aircraft of the American naval aviation.

Image copyright SPL Image caption Compaction shock when an aircraft enters supersonic sound is difficult to detect with the naked eye

Members of the US Navy Blue Angels aerobatic team fly in the same combat vehicles, skillfully performing maneuvers in which a condensation cloud forms around the aircraft.

Due to 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-Glauert effect are most optimal, and professional naval photographers are on duty nearby - after all, to take a clear picture jet planeflying at a speed of 960 km / h on a regular smartphone is impossible.

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

"The aircraft does not necessarily fly at supersonic speed, but the air flows around the top surface of its wing at a faster speed than the bottom, which leads to a local shock," says Irwin.

According to him, for the Prandtl-Glauert effect to occur, certain climatic conditions (namely, warm and humid air), which carrier-based aircraft 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 mistake for a sign of going to supersonic.

• You can read it on the website