Hypersonic arms race. Walking in five swings What is 1 swing in aviation
Hypersonic speed, "hypersound" is the most fashionable word in the missile and aviation sphere today. Like "nanotechnology" everywhere ten years ago. But what is this "hypersound", and how is it measured?
From subsonic to hypersound
The speed of sound in air has long been accepted as a reference point for a variety of scientific and practical measurements. For the first time, Aristotle mentioned this value as quite stable. He used it to compare and characterize the movement of bodies. The first person in history to break the sound barrier was in 1947 the American test pilot Charles Yeager on the Bell X-1 experimental aircraft. The first Soviet pilot, Captain Oleg Sokolovsky, accelerated to the speed of sound a year later - on the La-176, also experimental.
True, supersonic flights in the middle of the twentieth century were very conventional in today's terms. La-176 reached the speed of sound only in a gentle dive, and Bell X-1 for this did not go up into the sky at all, but with the help of a carrier aircraft, so as not to spend all the fuel on takeoff.
It is customary to call the range from 1 to 5 speeds of sound supersonic, but 5 "sound" speeds and further - this is the same "hypersound" that is being talked about so much today. True, so far it is mentioned most often in relation to missile weapons, because manned and unmanned aircraft moving at such speeds, for the most part, are piece test models.
The most characteristic representative of this category of flying machines is the American NASA X-43, which in the first half of the last decade became a relatively open compilation of all similar secret military developments of Russia and the United States, which began in the 1950s. This small drone has reached almost ten speeds of sound. True, for this, he (like the same Bell X-1 in 1947!) First flew into the air, being attached to the wing of a B-52 bomber, then ten seconds gaining speed with the help of a jet engine, after which for the same time planned and ended up drowning in the ocean ...
Sound speed and Mach number
When it comes to supersonic or hypersonic speeds, instead of the usual kilometers (or miles) per hour, some strange "Machs" begin to appear. For example - "the speed of the aircraft exceeded Mach 5.2". What is this unit of measurement and how to perceive it?
The so-called "Mach number" is named after Ernst Mach, an Austrian physicist. Being one of the founders of gas mechanics and having finished his life in the era of the first flying "whatnot", "heavenly slug", he could not even imagine that already at the end of the 1940s. jet fighters will come close to the sound barrier, and the unit of speed, named after him, will become part of the everyday life of aviators.
The Mach number, or M as it is also called, is not the most obvious thing to understand. One of the canonical interpretations sounds like this: “the ratio of the flow velocity at a given point of the gas flow to the local speed of sound propagation in a moving medium” ... However, let's try to explain it in understandable words, “on our fingers”.
It is extremely simplified (and very incorrect!) To say that the unit of the Mach number is the speed of sound. In other words, 1 Mach is conventionally equal to 340 meters per second or 1224 km / h. Accordingly, Mach 2 is conventionally 680 meters per second or 2448 km / h, and further, respectively. However, any teacher of gas dynamics for such an explanation will give you a full-fledged "bream" with Abramovich's textbook. For the Mach number is not speed in the classical sense - in the form of distance traveled in a period of time. This dimensionless unit, although tightly tied to the speed of sound in air, takes into account the fact that the speed of sound is not constant at all!
Most believe that the speed of sound in air is 340 meters per second. But the properties of air can be different. This means that the speed of sound propagation in it is also different! In the surface layer, it is really equal to the same 340 meters per second, but, for example, at altitudes of about ten kilometers, the speed is different due to the rarefaction of the air and low temperatures, and is already about 300 meters per second.
To overcome the sound barrier directly above the ground, the plane needs to reach a speed of 1224 km / h, and at an altitude of ten thousand meters, a speed of 1076 km / h is sufficient for this - 148 km / h less. The difference of about 13-14 percent is quite a lot and is of significant importance both for the engineers who design the aircraft and for the pilots who fly it. In other words, Mach 1 is the speed of sound at specific parameters of altitude and temperature, in which the plane is flying, "here and now."
Why do you need to measure speed in Machs?
The word "MACH" or the letter "M" appears on special speed indicators in the pilot's cabins - these instruments are often supplemented with instrument airspeed meters and are called "tachometers" in flight jargon. The "mahometer" limb is marked in conventional units - conditionally speaking, if its arrow points to the number 1, then the plane flies at the speed of sound at a given moment of time and at a given altitude. If the flight, suppose, passes low above the ground, then the actual speed at Mach 1 will be 1224 km / h, if at an altitude of ten thousand meters - 1076 km / h.
But a natural question arises - why does the pilot need the speed data from the "mahometer"? The fact is that the moment of crossing the sound barrier is associated with abrupt changes in the aerodynamic balance of the aircraft and requires increased attention in control. And this moment is precisely indicated by the "tachometer".
In the future, after "passing through one", this device is also necessary to assess the real situation, as they say, "online", because beyond the sound limit the machine behaves quite differently than before. Well, and finally, the indication of the real speed in Mach is needed to track the number M, designated by the creators of the aircraft, as its structural strength.
However, not every aircraft has a "mahometer". Actually, it is generally accepted that for flying machines that do not exceed speeds of about 400 km / h and altitudes of about 2–3 thousand kilometers, the conversion of speed to the number M is irrelevant - the plane behaves quite linearly and predictably in its standard subsonic operating speed range.
Mach 2.5 - how much is km / h or m / s? ..
- So there are general concepts about speed, that is, independent of the nature of the weather, etc.! What does this mean the speed of sound is 330 m / s! Supersonic is no more than 1 max (330 m / s), that is, yes, but over 660 m / s (2376 km / h), that is, (lo) from 1 max to 2 max is covered by a dynamo-kinetic shock wave (Cavitation) of a kind a after super-acceleration before and upon reaching hypersound, Cavitation is pulled out until the surrounding air mixture heats up and subsequently loses its density by almost 5 times, which indicates that (the aircraft) will reach a speed of over 10 mah (36,000 km / h) but at the same time, it is better to put a cavitator capable of covering the body (LO) with an electro-magnetic field, which will lead to safer flights both for himself (LO) and for the ego of the crew and passengers !!! And even when we talk about speeds similar to the speed of sound and above, we mean a stepwise increase in the speed value and not their growth in terms of exponential, that is, 1 max 330 m / s 2 max 660 m / s 3 max and more is from 3600 km / h or 1000 (990) m / s! And all the speed values above hypersound should have names that go beyond the usual scope of both designations and the speed itself !!! That is, sound, super sound, hyper sound, ultra sound, mega sound, etc. !!!
- Why write if it's not correct?
- 1 Mach - 330 m / s or 1080 km / h
2.5 M = 2700 km / hMAX NUMBER, the ratio of the speed of a body or a FLUID (gas or liquid) to the speed of sound in the environment. Thus, the Mach number equal to 1 expresses the local speed of SOUND. An airplane flying at a speed below Mach 1 is considered subsonic, that is, flying at a speed lower than the speed of sound. SUPERSONIC FLIGHT means flying at a speed greater than Mach 1. Mach numbers are named after Ernst MACH, who investigated supersonic speeds and shock waves.
http://dic.academic.ru/dic.nsf/ntes/5531/ Mach number - To understand the Mach number by non-specialists, it is very simplistic to say that the numerical expression of the Mach number depends, first of all, on the height of the half (the higher the height, the lower the speed of sound and the higher the Mach number). The Mach number is the true speed in the stream (that is, the speed at which air flows around, for example, an airplane) divided by the speed of sound in a particular medium, so the relationship is inversely proportional. At the ground, the speed corresponding to Mach 1 will be approximately 340 m / s (the speed with which people habitually consider the distance of an approaching thunderstorm, measuring the time from a flash of lightning to the thunder that has come down) or 1224 km / h. At an altitude of 11 km, due to a drop in temperature, the speed of sound is below about 295 m / s or 1062 km / h.
- 1 max is one speed of sound equal to 330 m / s = gt; Mach 2.5 is 835 m / s
- It is impossible to say without knowing the height.
The speed of sound in air at different altitudes above sea level. At 15 C and 760 mm Hg. Art. (101325 Pa) at sea level.
The speed of sound in air at different altitudes above sea level. At 15 C and 760 mm Hg. Art. (101325 Pa) at sea level. Height, m Speed of sound, m / s
0340,29
50340,10
100339,91
200339,53
300339,14
400338,76
500338,38
600337,98
700337,60
800337,21
900336,82
1000336,43
5000320,54
10000299,53
20000295,07
50000329,80
80000282,54
Have you ever wanted to become a pilot? Know that a goal without a plan is just a desire (words of the great classic Antoine de Saint-Exupery). It is worth noting that he was not only a writer, but also a professional pilot.
Absolutely all people associated with the sky take aerodynamics courses. This is the science of the movement of air (gas), which also studies the effect of this environment on streamlined objects. One of the sections of aerodynamics is the peculiarities of flight in supersonic aircraft. And here the student will see the letter M in all its glory. What does it mean?
Very brief reference
The Latin letter M in aerodynamics textbooks is nothing more than a Mach number. It denotes the ratio of the speed of the flow around an object (for example, an airplane) to the local speed of sound. It owes its name in aviation works to the Austrian scientist Ernst Mach. In scientific words it looks like this:
M= v/ a
Here, v is the speed of the incident flow, a is the local speed of sound. It is worth noting that the speed of the object is used in foreign sources, in contrast to domestic literature. A person who does not face this in professional activity is likely to have two questions. What is the local speed of sound? Why is the Mach number needed?
Ready for takeoff!
What is meant by the word sound? First of all, it is a wave. After all, it creates disturbances in the environment, which are transmitted to air molecules, and so on along the chain. Therefore, with increasing altitude, where the atmosphere is more rarefied, the sound wave will propagate at a lower speed. Accordingly, it is the local speed of sound that is present in the Mach number formula. All values for specific heights have already been calculated (special tables) - you just have to substitute. The freestream velocity is measured using air pressure transducers (APS), which are installed on all aircraft. Now we have all the data, which means we can easily calculate the Mach number. A fair question arises: "Why not just use the airspeed?" Don't forget, you're flying high M.
Three, two, one - let's go
The Mach number in aviation (and not only) plays a huge role. Almost all civilian, military and space shuttle pilots cannot do without it. This parameter is so important!
When the aircraft moves through space, the air molecules around it begin to "resent". If the aircraft speed is low (M<1,~ 400 км/ч, дозвуковые ВС), то плотность окружающей среды остается постоянной. Но, по мере увеличения кинетической энергии, часть её уходит на сжатие околосамолётного воздушного пространства. Этот эффект компрессии зависит от того, с какой силой летательный аппарат действует на молекулы воздуха. Чем выше скорость полёта, тем больше воздух сжимается.
At a transonic speed (~ 1190 km / h), small perturbations are transmitted to other molecules around the aircraft (it is easier to consider the wing surface), and at one point, when at some point the speed of the incident flow is equal to the local speed of sound (M = 1 , namely the flow, the aircraft can fly at a lower speed), a shock wave arises. Therefore, the difference in the design of fighters is so obvious: their wings, tail unit and fuselage, in comparison with subsonic aircraft.
On aircraft flying with M<1, но на высоких скоростях (современные пассажирские лайнеры), такая ситуация тоже может произойти, только переход на околозвуковую скорость приведёт к более сильной ударной волне, значительному увеличению лобового сопротивления, уменьшению подъёмной силы, потере управления и дальнейшему падению.
For such aircraft, the critical Mach number is indicated in the flight operations documents (RLE for domestic, FCOM for foreign). This is the lowest M value at which the incident flow in any part of the aircraft will reach the speed of sound (Mcr). That's the whole secret!
By the way, the most successful flying passengers of the Soviet Union traveled faster than modern ones. Don't believe me?
The new is the long forgotten old
Old men are faster than young! And it's not a joke. One old forgotten plane was once the flagship of the USSR aviation. His name was TU-144. It was (and still is) the world's first supersonic passenger airliner to fly commercial flights with a maximum speed of 2500 km / h. Although the Tu-144's flying career was short-lived, its fate was inextricably linked with the number M.
The second similar aircraft was the British-French "Concorde". It is noteworthy that they made their first flight with a difference of only two months. A good knowledge of aerodynamics will help passengers on commercial flights to forget about long flights across the Atlantic. And flights of aircrafts and spaceships will continue to inspire humanity to new discoveries.
Ernst Mach. An idealist with materialistic inclinations :-).
In today's short article, we will go over the theoretical foundations a little and touch on one of the most important characteristics of flying aircraft at high speeds, including supersonic ones.
Supersonic and Mach number... These two concepts are quite closely related and in our time there is probably not a single person who, in one way or another, has not heard of number M... Usually this term accompanies the characteristics of any supersonic (and even just high-speed) aircraft. And there are a lot of such planes in the world now and their number, I think, is unlikely to decrease :-).
But after all, not so long ago, the theory of supersonic flows was just a theory, moreover, making only the first steps. It began to acquire the fundamentals only about 140 years ago, when the German scientist and philosopher Ernst Mach began researching aerodynamic processes in the supersonic motion of bodies. During that period, he discovered and investigated some of the phenomena of supersonic aerodynamics, which later received their name in his honor. Among them is and Mach number.
An interesting fact is that in Soviet science (and in scientific literature, especially before the war and immediately after it), this term was often used either without decoding (just the number M, the word "Mach" was not used), or using a second surname - Mayevsky ... That is Mach-Mayevsky number.
All this was a consequence of our then ideological state. Ernst Mach, in his philosophical views (he was, according to V.I. Lenin, a "subjective idealist") did not really fit into the framework of Marxist-Leninist philosophy, and N.V. problems of external ballistics.
External ballistics- a science that studies the movement of bodies after they leave the device that gave them this movement, that is, for example, the flight of a projectile after it leaves the barrel of an artillery gun. At the same time, the projectile flies at a very high speed, including supersonic.
It is quite natural that N.V. Maievsky in his research and development (advanced for his time and later became fundamental) operated with a concept similar to Mach number, and 15 years earlier than his German counterpart.
And the most important thing (for the official ideology :-)) was that the Russian scientist was not a philosopher 🙂 and did not have views that contradict Marxist-Leninist science 🙂 ...
However, be that as it may, today perhaps the most important definition for supersonic is the name (or rather the surname :-)) of the German Ernst Mach. And in itself, this word has long ceased to be just a surname. Mach, he is a swing 🙂. Only speed, only flight 🙂 ...
Let's return, however, to the specifics. What is this the most number M, and why is it actually needed in aviation? After all, people used to fly to themselves at subsonic speeds without any Mach numbers, and even now the overwhelming majority of aircraft on the ground are subsonic. However, not everything is as simple as it looks :-).
For any flight of an apparatus heavier than air, one of its most important parameters is. There are plenty of ways to measure speed today :-). For example, the parameters of the aircraft movement relative to the air can be measured in the following ways: ultrasonic, thermodynamic, thermal, turbine, gauge.
And (that is, the speed over the earth) can be measured by the Doppler, correlation, radiation method, as well as by the method of sighting the earth's surface.
But the most, so to speak, simple and logical, long-used, and therefore, naturally, well-developed and familiar aerometric (more precisely, aerodynamic) method. It is used to measure the airspeed of the aircraft and Mach number.
However, this method has certain disadvantages. Its principle itself is quite simple, and we have already talked about it. The air running onto the aircraft, as a result of its movement, has some kinetic energy or, simply put, a high-speed pressure ( ρV² / 2).
Getting into the air pressure receiver (, or), it is inhibited, and its pressure turns into pressure on the membrane of the dial gauge. The faster the plane flies, the greater the high-speed pressure, the greater the speed shown by the arrow of the device. That is, it seems, everything is as if by notes.
But it was not there:-). While the aircraft is flying not very fast (up to about 400 km / h) and not too high (up to 2, 3 thousand), everything really unfolds simply and naturally. And then the notes start to lie :-) ...
Air interacts with the aerodynamic surfaces of the aircraft, thereby determining the parameters of its flight. And these parameters depend on the parameters of the state of air, like a gas, which, of course, depend on the conditions in which a given volume of gas is located.
For example, they fall with height. And the lower the density, the less will be the velocity head with which the incoming flow presses on the membrane of the speed indicator.
That is, it turns out that if the device in the cockpit shows the same speed at altitudes, for example, 2000 m and 10,000 m (), then in fact this means that the plane is 10,000 m relative to the air (and the ground, of course, also: - )) moves much faster (). All due to the fact that the air is rarefied at altitude.
Plus another thing, not quite, to put it mildly, convenient for flight, like compressibility. Air is a gas, and, like any gas, it can be compressed under certain conditions, thereby changing the parameters of its state. Such conditions appear when flowing around aerodynamic surfaces at sufficiently high flight speeds (formally, the countdown starts from 400 km / h).
Air ceases to be a homogeneous medium, the same in all directions, which it is considered (albeit rather approximately) for low-speed aircraft. Conditions are created for the occurrence of so-called shock waves, the velocities of the air flow in different sections of the aerodynamic surface (wing profile, for example) change, the point of application of aerodynamic forces shifts, that is, the nature of the flow itself changes and, ultimately, the controllability parameters of the aircraft. That is, speaking in "smart" terms of the theory of supersonic :-), a wave crisis begins.
However, we will talk about it later. In the meantime, it can be seen that all these processes depend on the parameters of the air environment and the technical and design properties of the aircraft itself.
To describe the aerodynamic properties of an aircraft in interaction with the environment, the speed of movement alone is not enough. Indeed, its measured value, which itself qualitatively depends on the parameters of this medium, does not always characterize the true flow pattern (as in the example above).
Here we need a criterion that would take into account the flow parameters “in itself” and, based on which, it would always be possible to correctly characterize the aerodynamic properties of the aircraft, regardless of the flight conditions.
When I say this, I mean it. number M... And I do not use the word "criterion" by chance. The fact is that Mach number Is, speaking in the language of physics, one of similarity criteria in gas dynamics.
The meaning of this slightly convoluted name is actually simple and is that if two or more physical systems have the same similarity criteria, equal in magnitude, this means that the systems under consideration are similar, that is, they are similar or, speaking quite simply (:-)), are the same.
In relation to our aviation case, it may look like this, for example. The air flow at two different heights (let's say the same 2000 and 10000 m), interacting with our aircraft - these are two physical systems.
However, if they are the same at these heights, then this does not mean at all that the indicated interaction will also be the same, but rather the opposite. That is, speed cannot be a similarity criterion, and these two systems in such a situation are not at all similar.
However, if we say that an airplane flies at different altitudes (and generally in different conditions) with the same Mach number, then it is quite legitimate to assert that the flow conditions and aerodynamic properties at these altitudes (under these conditions) will be the same.
It should be said here that this statement, despite its fidelity, is based, however, on considerable simplifications. The first is that Mach number, although the main criterion for similarity in gas dynamics for us, is not the only one. And the second comes from the definition of numbers M.
Ernst Mach, conducting his research, hardly thought about the application of their results in aviation :-). She simply did not exist then. The definition was purely scientific and physically accurate. Mach number Is a dimensionless quantity equal to the ratio of the flow velocity at a given point of the moving gas medium to the speed of sound at this point.
That is M = V / a, where V is the flow velocity in m / s and a is the speed of sound in m / s. Thus, the number M, as it were, takes into account the speed of movement plus the change in the parameters of the air environment through the speed of sound, which depends on these parameters.
Mach number dimensionless quantity. It is impossible to express it in units of speed, and its translation into linear speed is impractical due to the variability of the speed of sound. Aircraft speed using number M, can be expressed only qualitatively, that is, estimating how many times the speed of the aircraft is greater or less than the speed of sound.
In this case, the format for writing values can be either with the use of an equal sign or without it. For example, the record M3 (as well as M = 3) may mean that the speed of the aircraft exceeded the speed of sound three times.
Simplifications as applied to aviation consist in the fact that the flow rate is replaced by the speed of movement of a physical body in a gaseous medium, that is, we mean the movement of an aircraft. The speed of sound is the speed of sound at flight altitude. In this case, however, it is not taken into account that the flow near a body of complex shape, which the aircraft is :-), can have very different values near different parts of the surface of this body.
Index of the number M on the dashboard of the supersonic "Concorde" (lower right corner). Above him is a speed indicator.
However, despite the sufficient incorrectness of the simplifications, the concept of the Mahanashl number in aviation is very widespread. And not only on supersonic aircraft, for which information about number M, so to speak, are vital :-), but also on many modern subsonic aircraft.
After all, their speeds, albeit subsonic, are quite high. In addition, the practical flight heights are also rather big. Since the speed of sound decreases significantly with altitude, it becomes expedient to use at high altitudes when piloting Mach number.
There are at least two reasons for this. Firstly, because of the big difference, which I mentioned above (unnecessary errors, which are also very noticeable, are not needed by anyone :-)), and, secondly, for the possibility of assessing the approach of a wave crisis.
The fact is that for each type of aircraft its manifestations take place at certain values of the number M. In this regard, almost all modern liners have flight characteristics. Mach number constraints to ensure sustainable management. The pilot, when flying the aircraft, makes sure that this limit is not exceeded.
Indicator of indicated airspeed and M number (in the center) on the instrument panel of the Yak-42 aircraft.
Indicator of true airspeed and M number (center) on the dashboard of the Boeing-747.
In this way number M is not speed in its purest form, but, nevertheless, an important parameter that allows the crew to correctly assess flight conditions and carry out safe and accurate control of the aircraft.
For information on Mach number practically all modern high-speed aircraft have an indicator of the M number in the cockpit. In common parlance, it is sometimes called a makhmeter. In most cases, it is a pointer-type speed indicator. Such devices can give either only Mach number values, or can be combined (combined) with a speed indicator, true or indicated.
Number indicator M.
Speed indicator US-1600.
Indicator of true speed and number M USIM-I. This type of sign is on the MIG-25 aircraft.
Indicator of true speed and M number (top left) on the dashboard of the supersonic MIG-25.
Often pointers to the number M perform with special signaling device, which, at the right time, issues a warning to the crew about exceeding any threshold value of this number.
MS-1. M-number indicator with electrical signaling.
By its design and principle of operation, the pointer numbers M in general, it is similar. But to account for changes in conditions with height, a aneroid box that responds to pressure changes.
Kinematic diagram of the indicator of the number M.
The overwhelming majority of modern aircraft still fly subsonic. This mode corresponds to Mach number less than 0.8. The following flight modes, in which M takes values from 0.8 to 1.2, are combined under the name transonic. And when the M number changes from 1.0 to 5.0, then this is already pure supersonic, the zone of supersonic flight of modern military aircraft.
There are, however, specimens directly not related to the army, moreover, reaching speeds at which Mach number exceeds five units. This is already a hypersound zone. However, we will talk about these semi-exotic vehicles and the modes of their flight in the next articles of the general topic devoted to supersonic.
Until next time :-).
Photos are clickable.