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Sound barrier

Sound Barrier

a phenomenon that occurs in the flight of an aircraft or rocket at the time of transition from subsonic to supersonic flight speed in the atmosphere. When the speed of the aircraft approaches the speed of sound (1200 km / h) in the air, a thin area appears in front of it, in which there is a sharp increase in the pressure and density of the air medium. This compaction of the air in front of an airplane in flight is called a shock wave. On the ground, the passage of a shock wave is perceived as a pop, similar to the sound of a shot. Having exceeded, the plane passes through this area of \u200b\u200bincreased air density, as if piercing it - it overcomes the sound barrier. For a long time, overcoming the sound barrier seemed to be a serious problem in the development of aviation. To solve it, it was necessary to change the profile and shape of the aircraft wing (it became thinner and swept), to make the front part of the fuselage more pointed and to supply the aircraft with jet engines. For the first time the speed of sound was exceeded in 1947 by Ch. Yeager on an X-1 (USA) aircraft with a liquid-propellant rocket engine launched from a B-29 aircraft. In Russia, OV Sokolovsky was the first to overcome the sound barrier in 1948 on an experimental La-176 aircraft with a turbojet engine.

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

Sound barrier

a sharp increase in the resistance of the aerodynamic aircraft at Mach, the flight numbers M (∞) slightly exceeding the critical number M *. The reason is that at numbers M (∞)\u003e M * occurs, accompanied by the appearance of wave resistance. The coefficient of wave drag of aircraft increases very rapidly with an increase in the number M, starting from M (∞) \u003d M *.
Availability of Z. b. makes it difficult to achieve a flight speed equal to the speed of sound, and the subsequent transition to supersonic flight. For this, it turned out to be necessary to create aircraft with thin swept wings, which made it possible to significantly reduce resistance, and jet engines, in which the thrust increases with increasing speed.
In the USSR, a speed equal to the speed of sound was first achieved on a La-176 aircraft in 1948.

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

See what a "sound barrier" is in other dictionaries:

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

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

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

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

A sharp increase in aerodynamic drag when the aircraft flight speed approaches the speed of sound (exceeding the critical Mach value of the flight number). It is explained by a wave crisis accompanied by an increase in wave resistance. Overcome 3. ... ... Big Encyclopedic Polytechnic Dictionary

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

sound barrier - sound barrier - a sharp increase in the resistance of the aerodynamic aircraft at Mach flight numbers M∞, slightly exceeding the critical number M *. The reason is that for numbers M∞\u003e Encyclopedia "Aviation"

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

BARRIER, ah, husband. 1. Obstacle (kind of wall, crossbar), placed on the way (when jumping, running). Take b. (get over it). 2. Fence, fencing. B. boxes, balconies. 3. transfer. Obstruction, obstacle for which n. Natural river b. for ... ... Explanatory dictionary Ozhegova

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At present, the problem of "breaking the sound barrier" seems to be essentially the task of powerful power motors. If there is sufficient thrust to overcome the increase in drag encountered up to and directly on the sound barrier so that the aircraft can quickly pass through the critical speed range, then little difficulty should be expected. It might be easier for an aircraft to fly in the supersonic speed range than in the transition range between subsonic and supersonic speeds.

Thus, the situation is somewhat similar to that which prevailed at the beginning of this century, when the Wright brothers were able to prove the possibility of active flight because they had a light engine with sufficient thrust. If we had the proper engines, then supersonic flight would become fairly common. Until recently, overcoming the sound barrier in level flight was carried out only with the use of rather uneconomical propulsion systems, such as rocket and ramjet engines with very high fuel consumption. Experimental aircraft type X-1 and Sky-rocket are equipped with rocket enginesthat are reliable only for a few minutes of flight, or turbojets with afterburners, but at the time of this writing, there are several aircraft that can fly at supersonic speed for half an hour. If you read in the newspaper that an airplane "went through the sound barrier," it often means that it did so through a dive. In this case, gravity supplemented the lack of traction.

There is a strange phenomenon associated with these aerobatics that I would like to point out. Suppose the plane

approaches the observer at subsonic speed, dives, reaching supersonic speed, then exits the dive and continues flying at subsonic speed again. In this case, the observer on the ground often hears two loud booming sounds, rather quickly following each other: "Boom, boom!" Some scientists have proposed explanations for the origin of the double hum. Akeret in Zurich and Maurice Roy in Paris both suggested that the hum is due to the accumulation of sound impulses, such as engine noise, emitted while the plane is passing through sound speed. If the plane is moving towards the observer, then the noise emitted by the plane will reach the observer in a shorter period of time compared to the interval in which it was issued. Thus, there is always some accumulation of sound impulses, provided that the sound source moves towards the observer. However, if the sound source moves at a speed close to the speed of sound, then the accumulation is infinitely enhanced. This becomes obvious if we assume that all the sound emitted by a source moving at exactly the speed of sound directly towards the observer will reach the latter at one short moment in time, namely, when the sound source has approached the location of the observer. The reason is that the sound and the sound source will move at the same speed. If the sound moved during this time period with supersonic speed, then the sequence of perceived and emitted sound impulses would be reversed; the observer will distinguish the signals emitted later, before he perceives the signals emitted earlier.

The double hum process, in accordance with this theory, can be illustrated by the diagram in Fig. 58. Suppose that the plane is moving directly towards the observer, but with variable speed. The AB curve shows the movement of the aircraft over time. The angle of inclination of the tangent to the curve indicates the instantaneous speed of the aircraft. The parallel lines shown in the diagram indicate sound propagation; the angle of inclination in these lines corresponds to the speed of sound. First, the aircraft's speed is subsonic on the segment, then at the segment - supersonic, and finally, on the segment - subsonic again. If the observer is at the initial distance D, then the points shown on the horizontal line correspond to the sequence of perceived

Fig. 58. Distance-time diagram of an airplane flying at variable speed. Parallel lines with an angle of inclination in show the propagation of sound.

sound impulses. We see that the sound emitted by the airplane during the second passage of the sound barrier (point) reaches the observer earlier than the sound emitted during the first passage (point). At these two instants, the observer perceives impulses emitted during a limited period of time in an infinitely small time interval. Therefore, he hears a rumble like an explosion. Between the two sounds of hum, he simultaneously perceives three impulses emitted at different times by the plane.

In fig. 59 is a schematic illustration of the noise intensity that would be expected in this simplified case. It should be noted that the accumulation of sound pulses in the case of an approaching sound source is the same process known as the Doppler effect; however, the characteristic of the latter effect is usually limited to the change in pitch associated with the accumulation process. The intensity of the perceived noise is difficult to calculate because it depends on the mechanism of sound production, which is not well known. In addition, the process is complicated by the shape of the trajectory, possible echoes, and shock waves that are observed in different parts aircraft during flight, and the energy of which is converted into sound waves after the aircraft has reduced speed. In some

Fig. 59. Schematic representation of the intensity of the noise perceived by the observer.

in recent articles on this topic, the phenomenon of double hum, sometimes triple, observed in ultra-high-speed dives, is attributed to these shock waves.

The problem of "breaking the sound barrier" or "wall of sound" seems to thrill the public imagination (the English movie Breaking the Sound Barrier gives some insight into the challenges of flying through a single Mach); pilots and engineers discuss the problem both seriously and jokingly. The next "scientific talk" of transonic flight demonstrates an excellent combination of technical knowledge and poetic liberties:

We glided smoothly through the air at 540 miles per hour. I've always liked the little XP-AZ5601-NG for its easy operation and for the fact that the Prandtl-Reynolds indicator is hidden in the right corner at the top of the panel. I checked the instruments. Water, fuel, rpm, Carnot efficiency, ground speed, enthalpy. All OK. Heading 270 °. Combustion efficiency is normal - 23 percent. The old turbojet engine hummed calmly as always, and Tony's teeth barely rattled from its 17 doors, which he threw over the Schenectady. Only a thin trickle of oil was leaking from the engine. This is life!

I knew the plane's engine was good for speeds higher than anything we ever tried. The weather was so clear, the sky was so blue, the air was so calm that I could not resist and increased my speed. I slowly moved the lever forward one position. The regulator only swung slightly, and after five minutes or so, everything was calm. 590 mph. I pressed the lever again. Only two nozzles are clogged. I pressed on the narrow hole cleaner. Opened again. 640 mph. Quiet. The exhaust pipe almost bent completely, a few square inches still exposed on one side. My hands were itching on the lever, and I pressed it again. The plane accelerated to 690 miles per hour, passing through the critical segment without breaking a single window. The cockpit was getting warm, so I blew some more air into the vortex cooler. Mach 0.9! I've never flown faster. I could see a slight shake outside the porthole, so I adjusted the wing shape and it disappeared.

Tony was dozing now, and I blew smoke from his pipe. I could not resist and added another level of speed. In exactly ten minutes we caught up with Mach 0.95. Behind in the combustion chambers, the total pressure dropped devilishly. That was life! The Pocket indicator was showing red, but I didn't care. Tony's candle was still burning. I knew the gamma was zero, but I didn't care.

My head was spinning with excitement. A bit more! I put my hand on the lever, but just at that moment Tony reached out and his knee brushed against my hand. The lever jumped as much as ten levels! Fuck! The small plane shook its full length, and the colossal loss of speed threw Tony and me onto the panel. It felt like we hit a solid brick wall! I could see that the nose of the plane was crumpled. I looked at the tachometer and froze! 1.00! God, in an instant I thought, we are at the maximum! If I don't get him to slow down before he slips off, we will find ourselves in diminishing resistance! Too late! Mach 1.01! 1.02! 1.03! 1.04! 1.06! 1.09! 1.13! 1.18! I was desperate, but Tony knew what to do. In the blink of an eye, he gave back

move! Hot air rushed into the exhaust pipe, it was compressed in the turbine, again broke into the chambers, expanded the compressor. Fuel began to flow into the tanks. The entropy meter swung to zero. Mach 1.20! 1.19! 1.18! 1.17! We are saved. He slid backward, he shifted backward while Tony and I prayed that the flow divider would not stick. 1.10! 1.08! 1.05!

Fuck! We hit the other side of the wall! We're trapped! Not enough negative thrust to break through back!

While we cringed in fear of the wall, the tail of the little plane fell apart and Tony shouted, "Light the rocket boosters!" But they turned in the wrong direction!

Tony reached out and pushed them forward, Mach's lines streaming from his fingers. I set them on fire! The blow was overwhelming. We passed out.

When I came to my senses, our little plane, all twisted, was just passing through zero Mach! I pulled Tony out and we fell hard to the ground. The plane slowed down in the east. Seconds later, we heard a crash as if it had hit another wall.

Not a single screw was found. Tony started weaving the netting while I wandered off to MIT.

The textbook examines the issues of professional ethics of a psychologist in the implementation of various types of professional activity: psychological counseling, psychodiagnostics, psychological correction and psychotherapy. Using examples from practice, the problems of professional interaction of a psychologist with representatives of related professions (teachers, doctors, lawyers, social workers) are revealed.

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