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A hypersonic aircraft is an aircraft capable of flying at hypersonic speeds.
What is hypersonic speed
In aerodynamics, a quantity is often used that shows the ratio of the speed of a stream or body to the speed of sound. This ratio is called the Mach number, after the Austrian scientist Ernst Mach, who laid the foundations for the aerodynamics of supersonic speeds.
where M is the Mach number;
u is the speed of the air flow or body,
c s is the speed of sound propagation.
In the atmosphere, under normal conditions, the speed of sound is approximately 331 m/s. The speed of a body at 1 Mach corresponds to the speed of sound. Supersonic is called speed in the range from 1 to 5 M. If it exceeds 5 M, then this is already a hypersonic range. This division is conditional, since there is no clear boundary between supersonic and hypersonic speeds. So they agreed to count in the 70s of the twentieth century.
From the history of aviation
"Silbertvogel"
For the first time, they tried to create a hypersonic aircraft during the Second World War in Nazi Germany. The author of this project, which was called " Silbertvogel"(silver bird) was an Austrian scientist Eugen Senger. The aircraft also had other names: America Bomber», « Orbital Bomber», « Antipodal Bomber», « Atmosphere Skipper», « Ural Bomber". It was a rocket-plane bomber that could carry up to 30 tons of bombs. It was intended to bombard the United States and the industrial regions of Russia. Fortunately, in those days it was impossible to build such an aircraft in practice, and it remained only in the drawings.
North American X-15
In the 60s of the twentieth century, the first X-15 rocket plane in history was created in the United States, the main task of which was to study the conditions of flight at hypersonic speeds. This device was able to overcome a height of 80 km. The record was considered to be the flight of Joe Walker, performed in 1963, when an altitude of 107.96 km was reached and a speed of 5.58 M.
X-15 was suspended under the wing of the B-52 strategic bomber. At an altitude of 15 km, he separated from the carrier aircraft. At that moment, his own liquid-propellant rocket engine kicked in. It worked for 85 seconds and passed out. By this time, the speed of the aircraft had reached 39 m/s. At the highest point of the trajectory (apogee), the apparatus was already outside the atmosphere and was in weightlessness for almost 4 minutes. The pilot carried out the planned research, with the help of gas rudders sent the plane into the atmosphere and soon landed. The altitude record reached by the X-15 lasted almost 40 years, until 2004.
X-20 Dyna Soar
From 1957 to 1963 By order of the US Air Force, Boeing carried out the development of a manned space interceptor-reconnaissance-bomber X-20. The program was called X-20 Dyna-Soar. The X-20 was supposed to be launched into orbit at a height of 160 km by a launch vehicle. The speed of the aircraft was planned to be slightly lower than the first space one, so that it would not become a satellite of the Earth. From a height, the aircraft was supposed to "dive" into the atmosphere, descending to 60-70 km, and carry out either photographing or bombing. Then it rose again, but already to a height less than the original one, and again “dived” even lower. And so on until he landed at the airport.
In practice, several models of the X-20 were made, pilot-astronauts were trained. But for a number of reasons, the program was curtailed.
Project "Spiral"
In response to the program X-20 Dyna-Soar in the 1960s The Spiral project was launched in the USSR. It was a fundamentally new system. It was assumed that a powerful booster aircraft with air-jet engines, weighing 52 tons and 28 m long, accelerates to a speed of 6 M. A manned orbital aircraft weighing 10 tons and 8 m long starts from its “back” at an altitude of 28-30 km Both aircraft, taking off from the airfield together, could each individually carry out an independent landing. In addition, the accelerating aircraft with its hypersonic speed was also planned to be used as a passenger airliner.
Since new technologies were required to create such a hypersonic booster aircraft, the project provided for the possibility of using not a hypersonic, but a supersonic aircraft.
The whole system was developed in 1966 in the design bureau OKB-155 A.I. Mikoyan. Two versions of the model went through a full cycle of aerodynamic research at the Central Aerodynamic Institute. Professor N.E. Zhukovsky in 1965 - 1975 But to create an airplane still failed. And this program, like the American one, was curtailed.
Hypersonic aviation
By the beginning of the 70s. In the twentieth century, flights at supersonic speeds became commonplace for military aircraft. There were also supersonic passenger aircraft. Aerospace aircraft could pass through dense layers of the atmosphere at hypersonic speeds.
In the USSR, work on a hypersonic aircraft began at the Tupolev Design Bureau in the mid-70s. Research and design of an aircraft capable of speeds up to 6 M (TU-260) with a flight range of up to 12,000 km, as well as a hypersonic intercontinental aircraft TU-360, were carried out. Its flight range was to reach 16,000 km. A project was even prepared for a passenger hypersonic aircraft, designed to fly at an altitude of 28-32 km at a speed of 4.5-5 M.
But in order for aircraft to fly at supersonic speeds, their engines must have features of both aviation and space technology. Existing air-jet engines (WFD) that used atmospheric air had temperature limitations and could be used on aircraft whose speeds did not exceed 3 M. And rocket engines had to carry a large supply of fuel on board and were not suitable for long-term flights in the atmosphere.
It turned out that the most rational for a hypersonic aircraft is a ramjet engine (ramjet), in which there are no rotating parts, in combination with a turbojet engine (turbojet engine) for acceleration. It was assumed that for flights at hypersonic speeds, a ramjet on liquid hydrogen is most suitable. And an accelerating engine is a turbojet engine running on kerosene or liquid hydrogen.
For the first time, the X-43A unmanned vehicle was equipped with a ramjet engine, which, in turn, was installed on the Pegasus cruise launch vehicle.
On March 29, 2004, a B-52 bomber took off in California. When he reached a height of 12 km, X-43A started from him. At an altitude of 29 km, he separated from the launch vehicle. At that moment, his own ramjet was launched. He worked for only 10 seconds, but was able to develop a hypersonic speed of 7 Mach.
At the moment, the X-43A is the fastest aircraft in the world. It is capable of speeds up to 11230 km / h and can rise to a height of up to 50 km. But it's still an unmanned aerial vehicle. But the hour is not far off when hypersonic aircraft will appear, on which ordinary passengers will be able to fly.
General information
Flight at hypersonic speed is part of the supersonic flight regime and is carried out in a supersonic gas flow. Supersonic air flow is fundamentally different from subsonic and the dynamics of aircraft flight at speeds above the speed of sound (above 1.2 M) is fundamentally different from subsonic flight (up to 0.75 M, the speed range from 0.75 to 1.2 M is called transonic speed). ).
The determination of the lower limit of hypersonic speed is usually associated with the onset of the processes of ionization and dissociation of molecules in the boundary layer (BL) near the apparatus that moves in the atmosphere, which begins to occur at about 5 M. This speed is also characterized by the fact that a ramjet engine (“ RAMJET") with subsonic combustion of fuel ("SPVRD") becomes useless due to the extremely high friction that occurs when braking the passing air in this type of engine. Thus, in the hypersonic speed range, to continue the flight, it is possible to use only a rocket engine or a hypersonic ramjet (scramjet) with supersonic fuel combustion.
Flow Characteristics
While the definition of hypersonic flow (HJ) is rather controversial due to the lack of a clear boundary between supersonic and hypersonic flows, HJ can be characterized by certain physical phenomena that can no longer be ignored when considering, namely:
Thin layer of shock wave
As the speed and corresponding Mach numbers increase, the density behind the shock wave (SW) also increases, which corresponds to a decrease in volume behind the SW due to the conservation of mass. Therefore, the shock wave layer, i.e. the volume between the vehicle and the SW, becomes thin at high Mach numbers, creating a thin boundary layer (BL) around the vehicle.
Formation of viscous shock layers
Part of the large kinetic energy contained in the air flow, at M > 3 (viscous flow) is converted into internal energy due to viscous interaction. An increase in internal energy is realized in an increase in temperature. Since the pressure gradient directed along the normal to the flow within the boundary layer is approximately zero, a significant increase in temperature at high Mach numbers leads to a decrease in density. Thus, the PS on the vehicle surface grows and, at high Mach numbers, merges with a thin layer of the shock wave near the nose, forming a viscous shock layer.
The appearance of instability waves in the PS, which are not characteristic of sub- and supersonic flows
high temperature flow
The high-velocity flow at the frontal point of the vehicle (stagnation point or region) causes the gas to heat up to very high temperatures (up to several thousand degrees). High temperatures, in turn, create non-equilibrium chemical properties of the flow, which consist in the dissociation and recombination of gas molecules, ionization of atoms, chemical reactions in the flow and with the surface of the apparatus. Under these conditions, the processes of convection and radiative heat transfer can be significant.
Similarity parameters
It is customary to describe the parameters of gas flows by a set of similarity criteria, which allow one to reduce an almost infinite number of physical states into similarity groups and which allow one to compare gas flows with different physical parameters (pressure, temperature, velocity, etc.) with each other. It is on this principle that experiments in wind tunnels and the transfer of the results of these experiments to real aircraft are based, despite the fact that in wind tunnel experiments the size of models, flow rates, thermal loads, etc., can differ greatly from real flight modes, at the same time time, similarity parameters (Mach, Reynolds, Stanton numbers, etc.) correspond to flight ones.
For trans- and supersonic or compressible flow, in most cases such parameters as Mach number (ratio of flow velocity to local speed of sound) and Reynolds are sufficient to fully describe the flows. For a hypersonic flow, these parameters are often not enough. Firstly, the equations describing the shape of the shock wave become practically independent at speeds from 10 M. Secondly, the increased temperature of the hypersonic flow means that the effects related to non-ideal gases become noticeable.
Accounting for effects in a real gas means more variables that are required to fully describe the state of the gas. If a stationary gas is completely described by three quantities: pressure , temperature, heat capacity (adiabatic index), and a moving gas is described by four variables, which also includes speed , then a hot gas in chemical equilibrium also requires equations of state for its constituent chemical components, and a gas with processes dissociation and ionization must also include time as one of the variables of its state. In general, this means that at any given time, a non-equilibrium flow requires 10 to 100 variables to describe the state of the gas. In addition, rarefied hypersonic flow (HJ), usually described in terms of Knudsen numbers, does not obey the Navier-Stokes equations and requires their modification. HP is usually categorized (or classified) using total energy expressed using total enthalpy (mJ/kg), total pressure (kPa), and flow stagnation flow temperature (K) or speed (km/s).
Ideal gas
In this case, the passing air stream can be considered as an ideal gas stream. The HP in this mode still depends on the Mach numbers and the simulation is guided by temperature invariants , and not by the adiabatic wall , which occurs at lower speeds. The lower limit of this region corresponds to velocities around Mach 5, where the subsonic scramjet engine becomes ineffective, and the upper limit corresponds to speeds in the region of Mach 10-12.
Ideal gas with two temperatures
It is part of the case of the ideal gas flow regime with high velocities, in which the passing airflow can be considered chemically ideal, but the vibrational temperature and rotational temperature of the gas must be considered separately, resulting in two separate temperature models. This is of particular importance in the design of supersonic nozzles, where vibrational cooling due to molecular excitation becomes important.
dissociated gas
Beam transfer dominance mode
At velocities above 12 km/s, the heat transfer to the apparatus begins to occur mainly through ray transfer, which begins to dominate over thermodynamic transfer along with an increase in speed. Gas modeling in this case is divided into two cases:
- optically thin - in this case, it is assumed that the gas does not reabsorb radiation that comes from other parts of it or selected units of volume;
- optically thick - which takes into account the absorption of radiation by the plasma, which is then re-emitted, including on the body of the device.
Modeling optically thick gases is a difficult task, because due to the calculation of the radiative transfer at each point in the flow, the amount of calculations grows exponentially with the number of considered points.
10-07-2015, 11:34
What is behind the rumors about the creation of a new super-powerful weapon in Russia
The military-analytical center Janes Information Group (USA) has published a report on the successful testing by Russia of a new hypersonic aircraft Yu-71 (Yu-71 in English transcription).
Tests, according to the Americans, were carried out in February 2015. The launch allegedly took place from the Dombarovsky training ground near Orenburg. Their military analysts report top secret and bloodcurdling information to the common man in the street.
It is reported that the Yu-71 is part of the Russian secret project 4202. It was determined overseas that the speed of our hypersonic missile is 11,200 km/h. An object maneuvering at such a speed cannot be shot down - the missile defense system is powerless against such speeds. In addition, Yu-71 can carry a nuclear charge.
According to American analysts, Russia will soon be able to deliver high-precision strikes against selected targets. At the same time, even the most protected of them will be guaranteed to be hit by one missile. In the United States, it is assumed that in 5 years the deployment of a group of Russian hypersonic missiles will begin under the same Orenburg, in the Dombarovsky regiment of the Strategic Missile Forces stationed there, and in total from 2020 to 2025, 24 combat vehicles created on the basis of Yu-71 will be put into operation. It also follows from the document that by this time Russia will create a new heavy intercontinental ballistic missile "Sarmat", capable of carrying Yu-71.
It is argued that Moscow needs hypersonic weapons to gain leverage in negotiations with Washington and limit the effectiveness of the American missile defense system.
Prior to the publication of this sensation, it was reported that the Chinese military also conducted (and yet another) successful test of the WU-14 hypersonic attack aircraft capable of breaking through the US missile defense system and delivering a nuclear strike.
In general, the Americans were besieged from all sides: from the West - China, from the East and North - Russia. And they crave one thing - to break the American and European missile defense systems, like Tuzik a heating pad, in order to wipe out all the strategic objects of the Pentagon from the face of the earth. The logic of this horror is simple: Washington, give new billions to develop our own hypersonic missiles, otherwise we will remain undisguised, like the biblical Adam.
In the United States, work on hypersonic missiles is carried out with no less, if not more, intensity than in Russia and China combined. And with very good financial security.
Apparently, no breakthrough success has been achieved, and the billions allocated from the budget have already been spent. How to be? We need to launch a horror story and secure unlimited funding. Which is what was done.
The very idea of creating missiles capable of flying at 5-7, or even tens of times faster than the speed of sound, has always attracted the military. Such devices have such powerful kinetic energy that they are capable of causing the most serious damage to any enemy object even without a warhead. And with a nuclear warhead ...
In principle, it is not very difficult to disperse a warhead launched into near-Earth orbit to hypersonic and direct it downwards. The problem is in precise guidance, since it is not yet possible to control an object rushing at a speed of over 10,000 km / h. Including because with a sharp change in the rectilinear flight path, the warhead can simply collapse due to huge overloads.
And to build a workable device capable of flying at hypersonic speeds, and even maneuvering in the atmosphere, is incredibly difficult.
The point is not only in overloads, but also in the characteristics of fuel combustion, huge air friction on the surface of a flying vehicle, pressure surges on various surfaces of a hypersonic cruise missile.
Nevertheless, work in this direction has been carried out for several decades.
Closest to the practical creation of a cruise hypersonic missile came in the USSR. The Hypersonic Experimental Aircraft (GELA), or Kh-90, was created at the Raduga Design Bureau in the late 1980s. After the collapse of the USSR, the project was closed in 1992. Later, the GELA device was shown several times at the MAKS aerospace show in Zhukovsky.
By design, it was a cruise missile with a folding delta wing and a fuselage almost completely devoted to a ramjet engine. With a launch weight of 15 tons, the X-90 rocket, as its developers claimed, could accelerate to a speed of at least M = 4.5 - this is the minimum value of hypersound. According to reliable, but never officially confirmed data, the X-90 rocket was successfully launched from a carrier aircraft in the late 1980s, and it reached its design speed. Nevertheless, in the future, this project was not financed, and the very topic of hypersound was closed for more than 10 years.
Overseas, the creation of hypersonic aircraft went in parallel with work in the Soviet Union. True, without much success. The breakthrough was the Boeing X-43 project. Outwardly, the American aircraft was somewhat reminiscent of the closed Soviet X-90. In 2001, this hypersonic drone made its first flight, however, unsuccessful. The second flight is believed to have been normal. They did not reach superspeed, but they worked out the control system. But already on the third launch, in November 2004, the X-43 drone set a record, accelerating to a speed of 11,200 km / h. This is higher than our X-90 reached.
The development of the experimental project X-43 in the United States was the X-51 rocket. It is even more like our never-realized GELA project. It is argued that it is the X-51 that can become one of the main weapons of American strategic aviation. According to official data, the X-51 rocket should have a flight speed of the order of M = 6-7, which is close to the long-standing indicators of our X-90.
Such speeds, according to experts, are sufficient for the possible use of missiles in a fast global strike system. In 2010, the first launch and flight of the X-51 took place.