Hypersonic cruise missile : Everything you need to know

Military scientists are on the verge of developing a new type of flight and new aircraft

We are on the verge of developing a new type of flight and new aircraft – cruise missiles with the hypersonic engine. But the transition to serial samples is not yet possible, despite great efforts.

Hypersonic flight

Let me introduce you to hypersonic flight. The movement in a substance environment at a faster rate than sound in it is called supersonic. How much faster, shows a comparison with the local speed of sound. This comparison was called Mach’s number, dividing the speed of movement by the speed of sound and denoting it M. In supersonic flight the value of the Mach number is greater than one, for example 1.7 or 3. With such a number Of Mach fly supersonic aircraft. But the area of velocities with M 5 and more was isolated among the supersonic range and called hypersonic motion. At the standard speed of sound at the ground 340 m/s speed M q 5 will be 1700 m/s.

The first product of a person to reach hypersonic speed was the ballistic missile “Fau-2” Werner von Braun, which developed in flight speed just 1700 m/s. In the Pleistocene frost of the lower stratosphere, the speed of sound (and it depends on the temperature) is 295 m/s, so the number of Mach at “Fau-2” should rise to M 5.8. Later, hypersonic velocities reached a variety of tactical missiles with a range of 400-500 km. Some anti-aircraft missiles were dispersed to the hypersonic. For example, a liquid missile 5B28 anti-aircraft system S-200, which was therefore used for experiments with hypersonic engine on the themes “Cold” and “Igla.” High hypersonic speed developed missiles 53T6 Soviet anti-missile system A-135, the speed of which in the atmosphere, according to various data, reached M 13-18.

Tactical missiles (this range up to 500 km) and long-range warheads met hypersonic flow in the form of frontal resistance. Later, aero-ballistic missiles like the Iskander rockets began to be used to maneuver the lifting force of hypersonic flow, placing the smooth carrot of the missile at the angle of attack to the oncoming stream. So does the solid-fuel missile of the Dagger air complex, the aircraft version of the Iskander missile.

Space technology also passes the hypersonic section of the flight. The launch vehicles reach it in the upper atmosphere. The hypersonic lifting force is used by the Pegasus cruise missile, reaching the hypersonic in the upper stratosphere and having time to capture the triangular wing remnants of the rapidly melting atmosphere. The Space Shuttle, Buran and Soviet Bor series cruise vehicles entered the atmosphere at hypersonic speed. All of today’s returning spacecraft have a hypersonic section.

Thus, the movement at hypersonic speed today is not news or achievement, having been known in practice for almost 80 years. Hypersonics meet many types of aircraft during the stages of their flight. Some use hypersonic fairing as a normal supersonic, creating a lifting force with its cylindrical body or supersonic wing.

And only recently there were aircraft, the design of which is fully optimized for the creation of hypersonic lifting force, which became the main beginning, forming a trajectory. These devices are called hypersonic. These contraptions are made specifically for hypersonic flight and make the most of its features. They are grouped into two types, both as combat vehicles. The first is vehicles without an engine, or planning combat units. They can plan at hypersonic speeds for a range of up to a thousand kilometers. The second is hypersonic cruise missiles equipped with hypersonic air-jet engines similar to conventional cruise missiles. The design with a hypersonic engine is the most advanced, and it is called today hypersonic rocket in the most complete sense of the concept.

Differences in hypersonic flow

But why is the hypersonic area demarcated from supersonic? How is it different from supersonic and why the border was held at exactly five times the speed of sound, on M q 5? This boundary has a physical meaning, because behind it the flow becomes different.

In supersonic flight, the incoming stream is partially slowed down by the craft, squeezing against it and compacting. Compression increases the temperature of the air, and the stronger it is, the hotter the compressed air. The flow is most affected by parts of the apparatus that meet the air. Therefore, the front edges of the wings, stabilizers and keel, the other protruding parts in the stream are heated to several hundred degrees, for example up to 330 degrees at M q 3. Supersonic impact on the obstacle seems to crush a large supersonic speed on a myriad of tiny movements of molecules, small and multi-directional. Such a subtle grinding of movement translates kinetic energy into the inner, making it warm. Adding movement of molecules becomes heating, raising the temperature. But this heating is not reflected in the air molecules themselves, flying at simple points and colliding with each other with growing force.

The increasing flow rate amplifies the impact of molecules. In M, collisions are recalled in the molecules themselves. Two atoms in the molecules of the main gases of air, nitrogen and oxygen begin to resonate and oscillate, approaching and diverging. It’s a new, vibrational movement that’s got inside a molecule. The huge speed of the hypersonic flow increases the impact of the obstacle and its grinding, crushing kinetic energy before transforming into even smaller forms of movement – intramolecular. They add their energy to the molecule along with the beginning of another new movement, the rotation of molecules. These innovations are added to the heat intensity of the gas, stocking more heat and increasing the energy of the processes.

Pumping energy weakens the bonds of atoms moving away from each other in oscillations more and more, and molecules begin to disintegrate. Free atoms enter new compounds – chemical reactions flow. They multiply, fueled by the energy of the flow and catalytic effects of the materials of the device. Atoms lose electrons, plasma occurs, its concentration grows. The shock wave from the bow and the front edges bends more and more strongly and falls on the body, covering the entire aircraft. The wave merges with the surface layer, forming a single viscous shock boundary layer. The ceased to be ideal gas flows with cascades of unbalanced states, with high-frequency waves of instability and other complications. To adequately describe what is happening requires capacious mathematical constructions and hundreds of specific variables. Their values change all at once, at the same time as temperatures, pressures and concentrations, energies and balances of reactions and many other factors. All this is abundantly spiced with radiation and absorption ranging from thermal to ultraviolet and shines brightly from the surface of the device, strikingly different from simple supersonic compression and heating.

The jump of the seal

This is a very important supersonic concept that defines the flight of a hypersonic rocket and, like Elbrus, has two app tops, outside and inside the rocket. Often and universally it is confused with the shock wave, but it is not the same thing. The plume of sealing occurs in the supersonic stream as the inability to perturbate the air from any streamlined obstacles to dissolve forward. They move only at the speed of sound and accumulate in front of the source of disturbances, unable to escape from it up the supersonic stream. The stream pushes and tramples this accumulation of perturbations, creating a seal of air here. It occurs strongly and abruptly, leaping, at a distance of a couple of runs of molecules in ten billionths of a second. This instantaneous step of density growth is the plume leap.

And also hopping is the braking of the flow, instantly slowing down the speed and the current jump slower. Reducing the kinetic energy flow goes into increasing the potential energy of compression and heat. With the surge in density, the pressure and temperature also rise sharply. In the compaction jump, some of the flow energy is lost and expended, forming gas-dynamic losses. This causes an additional slowdown in the flow. Energy losses in horse racing are different, and you can work with this difference.

The jump of the seal is straight and oblique. A direct jump is perpendicular to the stream, “straight,” and slows the flow to the subsonic, completing the supersonic current. It has the biggest loss of energy. Oblique jumps lie at an angle to the stream, leave it supersonic and give less losses. If you need to slow down and compact the flow to a given amount, the compression in one jump will give more losses than the total two or three jumps weaker. Oblique plump compacts in the engine compress the air with a successive cascade with less energy loss, which is inexorably expended from the energy of the rocket’s motion, slowing it down.

There may be two roads behind the jump. If the reason for the jump is near – any hard surface at the angle of attack, wedge, cone, other forms – the air flows through it compressed. Behind the jump continues a compressed, heated and slowed flow. Then the plume jump is the front surface and the beginning of the compressed flow.

And when there is no indignant object behind the jump, for example in an open atmosphere, the compressed air after jump begins to expand unhindered. The greater the degree of compression, the more powerful the expansion. Its speed gives rise to inertia, and the expanding air slips through the parameters of the atmosphere without stopping at them. There is dilution, which soon collapses with the surrounding pressure of the atmosphere before alignment with itself.

Deviation from balance and subsequent free return to it is a wave process. And the whole structure – the plume jump, the area of compressed air behind it and the area of dilution – makes a shock wave. In it the plump of seal is only the front surface thick in the same pair of runs of molecules. The shock wave resembles a stack of two pancakes, compression and dilution, with a thin jump plum of seal on the front compression pancake.

In a hypersonic rocket, the seal jump works both inside and out. You could say he creates a hypersonic rocket by being its sculptor. The main work is the first way – the formation of compressed streams. They arise under the wings and hull from around the angle of attack and create the lifting force of the missile. The supersonic seal jump systems are organized inside the engine, ensuring that it works properly.

Flaming motor

The hot heart of a rocket is a hypersonic direct air-jet engine, or GPVRD. It compresses the oncoming air, burns fuel in it, pumping energy, and accelerates the jet nozzle, creating a jet stream and thrust. All this hypersonic engine makes its own, special way.

There is no compressor to compress the air. The incoming stream is compressed by its high speed, stystly by the surfaces of a tapering channel, or an embarrassment. The edges of the air intake are wedged into the air, driving it into the embarrassment. Any supersonic, with M zgt;1, the flow in the tapering running part is slowed down and compacted. Therefore, the PPPUR confusor has the appearance of a tapering funnel, rounded or slit-shaped with sloping faces. Here and work the races of the seal, which arises on the edges of the air intake. The air behind them flows in the form of a squeezed stream. Such jumps stand further in accordance with the geometry of the channel, consistently slowing down, compacting and heating the flow.

The conducer delivers multiple compressed hot air for combustion with a predetermined density and consumption. Density is necessary for sustainable combustion, consumption – for the level of traction. The compressed flow should remain supersonic, as at any point of the ERVRD. This is necessary to avoid large losses on the braking of the flow to the subsonic (then there will be a direct jump with the biggest losses) followed by the acceleration of its nozzle back to supersonic. To avoid needless losses, the flow throughout the engine is left supersonic. The confusion channel is carefully designed as an effective supersonic compression machine. It organizes compression control. In a compacted hot supersonic stream it remains only to spray the fuel and burn it. And meet two big problems of HGVRD.

Supersonic combustion is an extremely complex thing. Any ordinary flame will be blown off by supersonic, not having time to spread. We need another supersonic combustion mechanism. This is known – detonation. The shock wave of detonation is supersonic, and it compresses the substance to the heating needed combustion. The mixture of hydrogen and oxygen is called rattlesnake gas because it detonates very loudly, laying the ears before ringing. Adding hydrogen to the air, you can get rattlesnake gas, albeit heavily diluted with atmospheric nitrogen, but still capable of detonation.

The detonation wave of combustion will go through this mixture at supersonic speed. Here the plume leap works like a diesel piston, squeezing the mixture to ignition. If you equalize the speed of supersonic flow of air-hydrogen mixture at the speed of the detonation wave, the wave of combustion will run, remaining in place. And living this place of the running part as a combustion chamber. At a huge supersonic speed, it is necessary to adjust the flow and detonation rate in ultra-accurate way so that it does not go either forward or backwards from the combustion zone. Super-fast and super-fast, otherwise the wave will fly out of the chamber in a thousandth of a second. At the same time, it is important to accurately withstand the density, flow temperature, and a dozen other parameters – all affects the wave. Such management is a serious problem.

Fuel and the layout with it create a second big problem. Hydrogen is easier to mix with air, but kerosene or similar dense fuels should be sprayed to form a detonating mixture. Which one is made of fuel vapors or from thinly sprayed mist of small liquid droplets? Fuel fog detonation is a two-phase detonation system that works well in bulk blast munitions. The choice of detonation varieties is complicated by the search for fuel structures. Everything exposed in the supersonic stream outrages him, creating a surge of sealing. How to organize injectors or other spraying in the stream? How to prepare a high-quality supersonic fuel-air mixture, and in a very short time – a fraction of a millisecond? How to manage its composition with such speed? Fuel spraying, like a wall of supersonic combustion, is a very complex process and control. Here they are looking for key solutions to the effectiveness of ERVRD, which are not published in the press.

Finally, the detonation wave is behind, the gas is hotly burned in it fuel. Then he will have a jet nozzle. But this is not the usual nozzle of Laval. It does not have a tapering part – it is subsonic and is not needed here. Hot supersonic flow enters the immediately expanding supersonic nozzle. It is a diffuser, the usual expanding part of the familiar “rocket” nozzle of Laval, dispersing the jet jet and creating thrust.

The flow part of the PVRD thus resembles a pipe on both sides – narrowing of the embarrassment, combustion zone and expansion of the nozzle diffuser. The flow is everywhere supersonic, but at different speeds, the smallest in the central part. And this tune rattles its song high in the stratosphere.

Flight of the Bumblebee, or Game of Toece

The hypersonic engine immediately changes the aircraft, giving it great capabilities and creating a new combat vehicle from it. The range of a hypersonic missile can be much higher than the range of the glider. With more intensive maneuvering, the speed of the hypersonic rocket will not fall, supported by the engine. And this is directly combat quality – the degree of invulnerability for interception. Hypersonic cruise missile is harder to intercept because of its “range plus maneuvering plus speed” set of trumps, surpassing the hypersonic glider.

Maneuvering is the “armor” of a hypersonic missile, the main factor of invulnerability. Maneuvering prevents interception, constantly changing the sighting of anti-missiles and bringing them up close to critical flight modes, fraught with the termination of the chase. Anti-missiles are forced to constantly develop amendments of their guidance and change the flight, with the approach to the target more intensively, increasing their congestion to a critical level. The organization of anti-missile maneuvering can be based on different algorithms.

Let’s imagine that the flight control system virtually cuts off in front of a piece of the calculated trajectory of 10 or 15 kilometers. At the far end of this section, the control system draws a perpendicular flight square with sides of a couple of kilometers pierced by a trajectory in the center. The square is broken into equal cells, like nok crosses. Thus, the space in front of the rocket is split into a beam of diverging spatial segments stretching forward, each of which rests on its cell “cross-toe”.

As part of the flight control system, the random number generator is sewn up. He randomly throws his choice into one of the cells of “nok-no cells.” In the chosen cage draws a sighting cross, others remain zeros. After that, the control system directs the rocket into this randomly placed cross.

After flying the segment and being in a cage with a cross, thereby slightly shifted from the central spoke – the calculated trajectory, the control system cuts off from the further trajectory of the next piece, and the game repeats. At the end of the segment again drawn across the “nok-toe crosses”, strictly randomly put sighting cross.

Why is the choice of crosses strictly random? If there is any system in it, it can be “cracked” by more powerful computing tools and algorithms of the enemy, suggesting on a cruise missile their anti-missile. Future movements on any system can be correctly predicted and directed the interception tool to the correct point of the meeting. But the random choice can not be predicted.

Special logical blocks in the flight control system do not allow the missile to go beyond the two-kilometer square. Otherwise, step by step you can fly into deep deviations from the trajectory, critically removed from it. And then you can’t catch up with the calculated trajectory. Logical blocks monitor the ratio of local movements on “no-tod crosses” and the general direction of flight to the target. As a result, the movement of the cruise missile resembles a cross between the flight of a bumblebee and the rocking of a maple leaf, but performed in a hypersonic format. This makes it critically difficult to intercept a missile, but it doesn’t make it impossible – never say never.

The flight of a hypersonic missile consists of large geographical elements bypassing problem areas and anti-missile objects and imposed on them local anti-missile maneuvering, which can be enhanced by information about the launch of an anti-missile. Choosing architecture and maneuvering modes is a thorough and also not included in the wide information exchange.

Winged Hound Design

Intensive manoeuvres require a large lifting force, which can be tipped to turn the course of the rocket in different directions. Unlike subsonic and supersonic flight on hypersonic mode, the lifting force arises only due to the shock gas-dynamic compression of the flow on the lower surfaces of the spacecraft. It is compressed by the swings of seals on the wings and hull, arising from the angle of the attack. Compressed air flows from below surfaces and presses on them. Pressure forces gather in the lifting force of the apparatus.

The correct organization of compression zones and their parameters will determine the hypersonic aerodynamic quality of the rocket, its “volatility”. Sharp front edges reduce frontal resistance. The rocket receives a specialized gas-dynamic appearance – hypersonic. Its design is quite complex and requires a deep description of complex processes of hypersonic flow. This requires a deep understanding of them. We need large computing power, mathematical models with growing adequacy. Experimental measurements and data are needed. Therefore, the choice of rocket shapes, the balance of geometry and fairing, is also key and is a great value.

Multiple, up to dozens of times, degrees of air compression create high aerodynamic loads on the structure and great resistance. To reduce them, the flight takes place in very rarefied layers of the stratosphere, at altitudes of 25-30 km. This reduces the heat flow to the rocket, its heating at such a speed. The lower layers for hypersonic are always hotter. Therefore, the stratosphere becomes the main scene of a hypersonic rocket. There the rocket is lifted by a carrier – by plane or accelerating rocket stage. However, the accelerator is also needed at the aircraft launch to bring the hypersonic engine to the working modes of the current. Hypersonic it should get in the ready form, even the lowest range.

There is a navigation system, a flight control system and executive bodies to control the flight. The navigation system is formed by an inertial unit, astronautization and satellite navigation, the flight control system processes navigational and on-board data, from engine unit control to the shifting of the rocket center due to fuel production. It counts the management teams. Command lines carry them on engines, on the executives of orientation, such as the Aleron, and in other subsystems of the rocket, including the charge control unit, which transfers the charge in flight to an increasingly high degree of readiness for explosion.

The thermonuclear warhead of the hypersonic missile will be compact, the size of a bottle for the cooler, and weighing 200 kg. This compactness will not prevent the charge to allocate over the target all 150-300 kilotons of power written on its label. Tactical power of the charge is also possible, up to the non-nuclear warhead. Therefore, the hypersonic missile will cover a wide range of combat missions with high reliability, born of the chips of its flight.

What’s in practice

The first free flight with GVRD and acceleration in hypersonic range on its own thrust was performed by X-43A, an experimental NASA vehicle. It was launched by the Pegasus cruise missile, which was the most fully hypersonic cruise missile in these launches. After the acceleration of the device to the M 7, it separated, launched a hydrogen engine and then accelerated itself. In 2004, it reached a speed of M 9.6 or 3.2 km/s (data vary).

It was followed by a hypersonic X-51A Waverider cruise missile. Unlike the previous craft, it had the appearance of a cruise missile. In a successful test in 2013, the missile rose to 18 km and accelerated to M 5.1, passing 426 km in six minutes.

Now in the U.S. carry under the wing of the bomber hypersonic missile with GVRRD on hydrocarbon fuel. This is the first phase of HAWC testing. Flight tests of the missile are expected within the next year.

India this month launched an HSTDV cruise missile with a hypersonic engine. The solid-fuel rocket lifted it for 30 km and fell off, the device turned on the PVRD and accelerated to M 6. They tested the efficiency of the fuel system and the stability of fuel combustion.

Hypersonic cruise missiles are complex, requiring a powerful scientific and experimental base. But they are of great interest in terms of both weapons and technological upswing. There is no doubt that the development of these missiles will continue, and in the coming years hypersonic missiles with ERVRD will move out of the testing stage for mass production, adoption and the beginning of regular operation.