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What's the first thing that comes to mind when you hear the phrase "rocket engines"? Of course, mysterious space, interplanetary flights, the discovery of new galaxies and the alluring glow of distant stars. At all times, the sky has attracted people to itself, while remaining an unsolved mystery, but the creation of the first space rocket and its launch opened up new horizons of research for mankind.

Rocket engines are essentially ordinary jet engines with one important feature: to create jet thrust, they do not use atmospheric oxygen as a fuel oxidizer. Everything that is needed for its operation is located either directly in its body, or in the oxidizer and fuel supply systems. It is this feature that makes it possible to use rocket engines in outer space.

There are a lot of types of rocket engines and they all differ strikingly from each other not only in design features, but also in the principle of operation. That is why each type must be considered separately.

Among the main performance characteristics of rocket engines Special attention is given to the specific impulse - the ratio of the magnitude of jet thrust to the mass of the working fluid consumed per unit time. The specific impulse value reflects the efficiency and economy of the engine.

Chemical rocket engines (CRD)

This type of engine is currently the only one that is massively used for launching outer space spacecraft, in addition, it has found application in the military industry. Chemical engines are divided into solid and liquid fuel depending on state of aggregation rocket fuel.

History of creation

The first rocket engines were solid propellant, and they appeared several centuries ago in China. At that time, they had little to do with space, but with their help it was possible to launch military rockets. The fuel used was a powder, similar in composition to gunpowder, only percentage its constituents have been changed. As a result, during oxidation, the powder did not explode, but gradually burned out, releasing heat and creating jet thrust. Such engines were refined, improved and improved with varying success, but their specific impulse still remained small, that is, the design was inefficient and uneconomical. Soon, new types of solid fuels appeared that made it possible to obtain a greater specific impulse and develop greater traction. Scientists from the USSR, the USA and Europe worked on its creation in the first half of the 20th century. Already in the second half of the 1940s, a prototype of modern fuel was developed, which is still used today.

Rocket engine RD - 170 runs on liquid fuel and oxidizer.

Liquid rocket engines are an invention of K.E. Tsiolkovsky, who proposed them as a power unit for a space rocket in 1903. In the 1920s, work on the creation of a rocket engine began to be carried out in the USA, in the 1930s - in the USSR. Already by the beginning of World War II, the first experimental samples were created, and after its end, LRE began to be mass-produced. They were used in the military industry to equip ballistic missiles. In 1957, for the first time in the history of mankind, a Soviet artificial satellite. To launch it, a rocket equipped with Russian Railways was used.

The device and principle of operation of chemical rocket engines

A solid propellant engine contains in its body fuel and an oxidizer in a solid state of aggregation, and the fuel container is also a combustion chamber. The fuel is usually in the form of a rod with a central hole. During the oxidation process, the rod begins to burn from the center to the periphery, and the gases obtained as a result of combustion exit through the nozzle, forming thrust. This is the simplest design among all rocket engines.

In liquid propellant engines, the fuel and oxidizer are in a liquid state of aggregation in two separate tanks. Through the supply channels, they enter the combustion chamber, where they are mixed and the combustion process takes place. Combustion products exit through the nozzle, forming thrust. Liquid oxygen is usually used as an oxidizer, and the fuel can be different: kerosene, liquid hydrogen, etc.

Pros and cons of chemical RD, their scope

The advantages of solid propellant RD are:

simplicity of design;
comparative safety in terms of ecology;
low price;
reliability.

Disadvantages of RDTT:

limitation on operating time: fuel burns out very quickly;
the impossibility of restarting the engine, stopping it and regulating traction;
small specific gravity within 2000-3000 m/s.

Analyzing the pros and cons of solid propellant rocket motors, we can conclude that their use is justified only in cases where a medium power power unit is needed, which is quite cheap and easy to implement. The scope of their use is ballistic, meteorological missiles, MANPADS, as well as side boosters of space rockets (they are equipped with American missiles, they were not used in Soviet and Russian missiles).

Advantages of liquid RD:

high specific impulse (about 4500 m/s and above);
the ability to control traction, stop and restart the engine;
lighter weight and compactness, which makes it possible to launch even large multi-ton loads into orbit.

LRE disadvantages:

complex design and commissioning;
in weightless conditions, liquids in tanks can move randomly. For their deposition it is necessary to use additional sources of energy.

The scope of LRE is mainly astronautics, since these engines are too expensive for military purposes.

Despite the fact that so far chemical rocket engines are the only ones capable of ensuring the launch of rockets into outer space, their further improvement is practically impossible. Scientists and designers are convinced that the limit of their capabilities has already been reached, and other sources of energy are needed to obtain more powerful units with a high specific impulse.

Nuclear rocket engines (NRE)

This type of rocket engine, unlike chemical engines, generates energy not by burning fuel, but by heating the working fluid with energy. nuclear reactions. NRE are isotopic, thermonuclear and nuclear.

History of creation

The design and principle of operation of the NRE were developed back in the 50s. Already in the 70s, experimental samples were ready in the USSR and the USA, which were successfully tested. The solid-phase Soviet engine RD-0410 with a thrust of 3.6 tons was tested on a bench base, and the American NERVA reactor was to be installed on the Saturn V rocket before sponsorship lunar program was stopped. In parallel, work was also carried out on the creation of gas-phase NREs. Now active science programs on the development of nuclear RD, experiments are being carried out at space stations.

Thus, there are already working models of nuclear rocket engines, but so far none of them has been used outside of laboratories or scientific bases. The potential of such engines is quite high, but the risk associated with their use is also considerable, so for now they exist only in projects.

Device and principle of operation

Nuclear rocket engines are gas-, liquid- and solid-phase, depending on the state of aggregation of nuclear fuel. Fuel in solid-phase NREs is fuel rods, the same as in nuclear reactors. They are located in the engine case and in the process of decay of fissile material they release thermal energy. The working fluid - gaseous hydrogen or ammonia - in contact with the fuel element, absorbs energy and heats up, increasing in volume and shrinking, after which it exits through the nozzle under high pressure.

The principle of operation of a liquid-phase NRE and its design are similar to solid-phase ones, only the fuel is in a liquid state, which makes it possible to increase the temperature, and hence the thrust.

Gas-phase NREs operate on fuel in gaseous state. They usually use uranium. Gaseous fuel can be retained in the housing electric field or is located in a sealed transparent flask - a nuclear lamp. In the first case, there is a contact of the working fluid with the fuel, as well as a partial leakage of the latter, therefore, in addition to the bulk of the fuel, the engine must have its reserve for periodic replenishment. In the case of a nuclear lamp, there is no leakage, and the fuel is completely isolated from the flow of the working fluid.

Advantages and disadvantages of YARD

Nuclear rocket engines have a huge advantage over chemical ones - this is a high specific impulse. For solid-phase models, its value is 8000-9000 m/s, for liquid-phase models it is 14000 m/s, for gas-phase models it is 30000 m/s. However, their use entails pollution of the atmosphere. radioactive emissions. Now work is underway to create a safe, environmentally friendly and efficient nuclear engine, and the main "candidate" for this role is a gas-phase NRE with a nuclear lamp, where radioactive substance is in a sealed flask and does not go outside with a jet flame.

Electric rocket engines (EP)

Another potential competitor to chemical rocket engines is an electric rocket engine powered by electrical energy. ERD can be electrothermal, electrostatic, electromagnetic or pulsed.

History of creation

The first EJE was designed in the 30s Soviet designer V.P. Glushko, although the idea of creating such an engine appeared in the early twentieth century. In the 60s, scientists from the USSR and the USA were actively working on the creation of an EJE, and already in the 70s, the first samples began to be used in spacecraft as control engines.

Device and principle of operation

An electric propulsion system consists of the EJE itself, the structure of which depends on its type, the systems for supplying the working fluid, control and power supply. Electrothermal RD heats the flow of the working fluid due to the heat generated by the heating element, or in an electric arc. Helium, ammonia, hydrazine, nitrogen and other inert gases, less often hydrogen, are used as a working fluid.

Electrostatic RD are divided into colloidal, ionic and plasma. In them, the charged particles of the working fluid are accelerated by the electric field. In colloidal or ionic RDs, gas ionization is provided by an ionizer, a high-frequency electric field, or a gas-discharge chamber. In plasma RDs, the working fluid, xenon, an inert gas, passes through an annular anode and enters a gas-discharge chamber with a compensating cathode. At high voltage a spark flashes between the anode and cathode, ionizing the gas, resulting in a plasma. Positively charged ions exit through the nozzle at a high speed, acquired due to acceleration by an electric field, and electrons are brought out by a compensating cathode.

Electromagnetic RD have their own magnetic field - external or internal, which accelerates the charged particles of the working fluid.

Impulse RD work due to the evaporation of solid fuel under the action of electrical discharges.

Advantages and disadvantages of ERD, scope of use

Among the advantages of ERD:

high specific impulse, upper limit which is practically unlimited;
low fuel consumption (working fluid).

Disadvantages:

high level electricity consumption;
design complexity;
little traction.

To date, the use of electric propulsion is limited to their installation on space satellites, and as sources of electricity for them are used solar panels. At the same time, it is these engines that can become those power plants that will make it possible to explore space, therefore, work on the creation of their new models is being actively carried out in many countries. Exactly these power plants most often mentioned by science fiction writers in their works devoted to the conquest of space, they can also be found in science fiction films. So far, it is the ERD that is the hope that people will still be able to travel to the stars.

How a liquid-propellant engine works and works

Liquid-propellant engines are currently used as engines for heavy rocket projectiles. air defense, long-range and stratospheric missiles, rocket planes, rocket air bombs, aerial torpedoes, etc. Sometimes rocket engines are also used as starting engines to facilitate the take-off of aircraft.

Keeping in mind the main purpose of LRE, we will get acquainted with their design and operation using two engines as examples: one for a long-range or stratospheric rocket, the other for a rocket aircraft. These particular engines are by no means typical and, of course, inferior in their data to the latest engines of this type, but they are still characteristic in many ways and give a fairly clear idea of \u200b\u200bthe modern liquid-propellant engine.

LRE for long-range or stratospheric rocket

Rockets of this type were used either as a long-range super-heavy projectile or for exploring the stratosphere. For military purposes, they were used by the Germans to bomb London in 1944. These missiles had about a ton of explosive and a flight range of about 300 km. When exploring the stratosphere, the rocket head carries various research equipment instead of explosives and usually has a device for separation from the rocket and parachute descent. Rocket lift height 150–180 km.

The appearance of such a rocket is shown in Fig. 26, and its section in Fig. 27. The figures of people standing next to the rocket give an idea of the impressive size of the rocket: its total length is 14 m, diameter about 1.7 m, and plumage about 3.6 m, the weight of an equipped rocket with explosives is 12.5 tons.

Fig. 26. Preparing to launch a stratospheric rocket.

The rocket is propelled by a liquid-propellant engine located at its rear. General form engine is shown in Fig. 28. The engine runs on two-component fuel - ordinary wine (ethyl) alcohol 75% strength and liquid oxygen, which are stored in two separate large tanks, as shown in Fig. 27. The stock of fuel on the rocket is about 9 tons, which is almost 3/4 of the total weight of the rocket, and in terms of volume, the fuel tanks are most the entire volume of the rocket. Despite such a huge amount of fuel, it is only enough for 1 minute of engine operation, since the engine consumes more than 125 kg fuel per second.

Fig. 27. A section of a long-range missile.

The amount of both fuel components, alcohol and oxygen, is calculated so that they burn out simultaneously. Since for combustion 1 kg alcohol in this case consumes about 1.3 kg oxygen, the fuel tank holds approximately 3.8 tons of alcohol, and the oxidizer tank holds about 5 tons of liquid oxygen. Thus, even in the case of using alcohol, which requires significantly less oxygen for combustion than gasoline or kerosene, filling both tanks with fuel alone (alcohol) when using atmospheric oxygen would increase the duration of the engine by two to three times. This is where the need to have an oxidizer on board a rocket comes in.

Fig. 28. Rocket engine.

The question involuntarily arises: how does a rocket cover a distance of 300 km if the engine runs for only 1 minute? This is explained in Fig. 33, which shows the trajectory of the rocket, as well as the change in speed along the trajectory.

The launch of the rocket is carried out after placing it in a vertical position with with the help of a lung trigger, as seen in Fig. 26. After launch, the rocket initially rises almost vertically, and after 10–12 seconds of flight, it begins to deviate from the vertical and, under the action of rudders controlled by gyroscopes, moves along a trajectory close to the arc of a circle. Such a flight lasts all the time while the engine is running, that is, for about 60 seconds.

When the speed reaches the calculated value, the control devices turn off the engine; by this time, there is almost no fuel left in the rocket tanks. The height of the rocket at the end of the engine is 35–37 km, and the axis of the rocket makes an angle of 45° with the horizon (point A in Fig. 29 corresponds to this position of the rocket).

Fig. 29. The flight path of a long-range missile.

This elevation angle provides maximum range in the subsequent flight, when the rocket moves by inertia, like an artillery shell that would fly out of a gun with a sawn-off barrel at a height of 35–37 km. The trajectory of further flight is close to a parabola, and total time flight is approximately 5 minutes. The maximum height that the rocket reaches in this case is 95-100 km, stratospheric rockets reach much higher altitudes, more than 150 km. In photographs taken from this height by a device mounted on a rocket, the sphericity of the earth is already clearly visible.

It is interesting to see how the flight speed along the trajectory changes. By the time the engine is turned off, i.e. after 60 seconds of flight, the flight speed reaches the greatest value and is equal to approximately 5500 km/h, i.e. 1525 m/s. It is at this moment that the power of the engine also becomes the greatest, reaching for some rockets almost 600,000 l. with.! Further, under the influence of gravity, the speed of the rocket decreases, and after reaching highest point For the same reason, the trajectory begins to grow again until the rocket enters the dense layers of the atmosphere. During the entire flight, except for the very initial phase - acceleration - the speed of the rocket significantly exceeds the speed of sound, average speed along the entire trajectory is approximately 3500 km/h and even on the ground, the rocket falls at a speed two and a half times the speed of sound and equal to 3000 km/h. This means that the powerful sound from the flight of the rocket is heard only after it has fallen. Here it will no longer be possible to catch the approach of a rocket with the help of sound pickups, usually used in aviation or navy, this will require completely different methods. Such methods are based on the use of radio waves instead of sound. After all, a radio wave propagates at the speed of light - the highest speed possible on earth. This speed of 300,000 km/sec is, of course, more than sufficient to mark the approach of the fastest rocket.

Another problem is related to the high speed of rocket flight. The fact is that at high flight speeds in the atmosphere, due to braking and compression of the air running on the rocket, the temperature of its body rises greatly. The calculation shows that the temperature of the walls of the rocket described above should reach 1000–1100 °C. Tests showed, however, that in reality this temperature is much lower due to the cooling of the walls by thermal conduction and radiation, but nevertheless it reaches 600–700 ° C, i.e., the rocket heats up to a red heat. As the rocket's flight speed increases, the temperature of its walls will rise rapidly and may become a serious obstacle to a further increase in flight speed. Recall that meteorites (heavenly stones) bursting from great speed, up to 100 km/s, within earth's atmosphere, as a rule, "burn out", and what we take for a falling meteorite ("shooting star") is in reality only a clot of hot gases and air, formed as a result of the movement of a meteorite at high speed in the atmosphere. Therefore, flights with very high speeds are possible only in the upper layers of the atmosphere, where the air is rarefied, or outside it. The closer to the ground, the lower the permissible flight speeds.

Fig. 30. Scheme of the rocket engine.

The rocket engine diagram is shown in Fig. 30. Noteworthy is the relative simplicity of this scheme compared to conventional piston aircraft engines; in particular, LRE is characterized by the almost complete absence of moving parts in the power circuit of the engine. The main elements of the engine are a combustion chamber, a jet nozzle, a steam generator and a turbopump unit for fuel supply and a control system.

Fuel combustion occurs in the combustion chamber, i.e., the conversion of the chemical energy of the fuel into thermal energy, and in the nozzle, the thermal energy of the combustion products is converted into the high-speed energy of the gas jet flowing from the engine into the atmosphere. How the state of gases changes during their flow in the engine is shown in Fig. 31.

The pressure in the combustion chamber is 20–21 ata, and the temperature reaches 2,700 °C. Characteristic of the combustion chamber is a huge amount of heat that is released in it during combustion per unit time or, as they say, the heat density of the chamber. In this regard, the LRE combustion chamber is significantly superior to all other combustion devices known in the art (boiler furnaces, engine cylinders). internal combustion other). In this case, in the combustion chamber of the engine per second, such an amount of heat is released that is sufficient to boil more than 1.5 tons ice water! So that the combustion chamber with such huge number the heat released in it has not failed, it is necessary to intensively cool its walls, as well as the walls of the nozzle. For this purpose, as seen in FIG. 30, the combustion chamber and nozzle are cooled by fuel - alcohol, which first washes their walls, and only then, heated, enters the combustion chamber. This cooling system, proposed by Tsiolkovsky, is also beneficial because the heat removed from the walls is not lost and returns to the chamber again (this is why such a cooling system is sometimes called regenerative). However, external cooling of the engine walls alone is not enough, and cooling of the walls is simultaneously applied to lower the temperature of the walls. inner surface. For this purpose, the walls in a number of places have small holes located in several annular belts, so that through these holes alcohol enters the chamber and nozzle (about 1/10 of its total consumption). The cold film of this alcohol, flowing and evaporating on the walls, protects them from direct contact with the flame of the torch and thereby reduces the temperature of the walls. Despite the fact that the temperature of the gases washing from the inside of the walls exceeds 2500 °C, the temperature of the inner surface of the walls, as tests have shown, does not exceed 1000 °C.

Fig. 31. Change in the state of gases in the engine.

Fuel is supplied to the combustion chamber through 18 prechamber burners located on its end wall. Oxygen enters the prechambers through the central nozzles, and alcohol leaving the cooling jacket through a ring of small nozzles around each prechamber. This provides a sufficiently good mixing of the fuel necessary for the implementation of complete combustion for a very a short time while the fuel is in the combustion chamber (hundredths of a second).

The jet nozzle of the engine is made of steel. Its shape, as can be clearly seen in Fig. 30 and 31, is first a narrowing and then expanding pipe (the so-called Laval nozzle). As mentioned earlier, nozzles and powder rocket engines have the same shape. What explains this shape of the nozzle? As you know, the task of the nozzle is to provide full expansion gas in order to obtain the highest exhaust velocity. To increase the speed of gas flow through a pipe, its cross section must first gradually decrease, which also occurs with the flow of liquids (for example, water). The gas velocity will increase, however, only until it becomes equal speed propagation of sound in a gas. A further increase in velocity, in contrast to a liquid, will only be possible with the expansion of the pipe; this difference between gas flow and liquid flow is due to the fact that the liquid is incompressible, and the volume of the gas increases greatly during expansion. In the throat of the nozzle, i.e., in its narrowest part, the gas flow velocity is always equal to the speed of sound in the gas, in our case, about 1000 m/s. The outflow velocity, i.e., the velocity in the outlet section of the nozzle, is 2100–2200 m/s(thus the specific thrust is approximately 220 kg sec/kg).

The supply of fuel from the tanks to the combustion chamber of the engine is carried out under pressure by means of pumps driven by a turbine and arranged together with it into a single turbopump unit, as can be seen in Fig. 30. In some engines, the fuel supply is carried out under pressure, which is created in sealed fuel tanks with the help of some inert gas - for example, nitrogen, stored under high pressure in special cylinders. Such a supply system is simpler than a pumping one, but, with a sufficiently large engine power, it turns out to be heavier. However, even when pumping fuel in the engine we are describing, the tanks, both oxygen and alcohol, are under some overpressure from the inside to facilitate the operation of the pumps and to prevent the tanks from collapsing. This pressure (1.2–1.5 ata) is created in the alcohol tank with air or nitrogen, in the oxygen tank - with vapors of evaporating oxygen.

Both pumps are centrifugal type. The turbine that drives the pumps runs on a steam-gas mixture resulting from the decomposition of hydrogen peroxide in a special steam-gas generator. Sodium permanganate, which is a catalyst that accelerates the decomposition of hydrogen peroxide, is fed into this steam and gas generator from a special tank. When a rocket is launched, hydrogen peroxide under nitrogen pressure enters the steam-gas generator, in which a violent reaction of peroxide decomposition begins with the release of water vapor and gaseous oxygen(this is the so-called "cold reaction", which is sometimes used to create thrust, in particular, in starting rocket engines). Vapor-gas mixture having a temperature of about 400 °C and pressure over 20 ata, enters the turbine wheel and then is released into the atmosphere. The power of the turbine is spent entirely on the drive of both fuel pumps. This power is not so small already - at 4000 rpm of the turbine wheel, it reaches almost 500 l. with.

Since a mixture of oxygen and alcohol is not a self-reactive fuel, some kind of ignition system must be provided to start combustion. In the engine, ignition is carried out using a special fuse, which forms a flame torch. For this purpose, a pyrotechnic fuse (a solid igniter such as gunpowder) was usually used, and a liquid igniter was less commonly used.

Rocket launch is carried out as follows. When the ignition torch is ignited, the main valves are opened, through which alcohol and oxygen enter the combustion chamber by gravity from the tanks. All valves in the engine are controlled by compressed nitrogen stored on the rocket in a cylinder battery high pressure. When the combustion of the fuel begins, an observer located at a distance, using an electrical contact, turns on the supply of hydrogen peroxide to the steam and gas generator. The turbine begins to work, which drives the pumps that supply alcohol and oxygen to the combustion chamber. The thrust grows and when it becomes more than the weight of the rocket (12-13 tons), the rocket takes off. From the moment the ignition flame is ignited to the moment the engine develops full thrust, only 7-10 seconds pass.

When starting up, it is very important to ensure strict order both fuel components enter the combustion chamber. This is one of the important tasks of the engine control and regulation system. If one of the components accumulates in the combustion chamber (because the intake of the other is delayed), then an explosion usually follows this, in which the engine often fails. This, along with occasional interruptions in combustion, is one of the most common causes catastrophes during LRE tests.

Noteworthy is the negligible weight of the engine compared to the thrust it develops. When the engine weight is less than 1000 kg thrust is 25 tons, so that the specific gravity of the engine, i.e., the weight per unit of thrust, is only

For comparison, we indicate that a conventional piston aircraft engine running on a propeller has a specific gravity of 1–2 kg/kg, i.e., several tens of times more. It is also important that the specific gravity of a rocket engine does not change with a change in flight speed, while the specific gravity of a piston engine increases rapidly with increasing speed.

LRE for rocket aircraft

Fig. 32. Project LRE with adjustable thrust.

1 - mobile needle; 2 - mechanism for moving the needle; 3 - fuel supply; 4 - oxidant supply.

The main requirement for an aircraft liquid-propellant engine is the ability to change the thrust it develops in accordance with the flight modes of the aircraft, up to stopping and restarting the engine in flight. The simplest and most common way to change the thrust of an engine is to regulate the supply of fuel to the combustion chamber, as a result of which the pressure in the chamber and thrust change. However, this method is unfavorable, since with a decrease in pressure in the combustion chamber, which is lowered in order to reduce thrust, the proportion of thermal energy of the fuel that passes into the high-speed energy of the jet decreases. This results in an increase in fuel consumption by 1 kg thrust, and consequently, by 1 l. with. power, i.e., the engine starts to work less economically. To reduce this shortcoming, aircraft rocket engines often have two to four combustion chambers instead of one, which makes it possible to turn off one or more chambers when operating at reduced power. Thrust control by changing the pressure in the chamber, i.e., by supplying fuel, is retained in this case as well, but is used only in a small range up to half the thrust of the chamber being switched off. The most advantageous way to regulate the thrust of a liquid-propellant rocket engine would be to change the flow section of its nozzle while reducing the fuel supply, since in this case a decrease in the per second amount of escaping gases would be achieved while maintaining the same pressure in the combustion chamber, and, hence, the exhaust velocity. Such regulation of the nozzle flow area could be carried out, for example, using a movable needle of a special profile, as shown in Fig. 32, depicting the design of a liquid-propellant rocket engine with thrust regulated in this way.

In FIG. 33 shows a single-chamber aircraft rocket engine, and Fig. 34 - the same rocket engine, but with an additional small chamber, which is used in cruise flight when little thrust is required; the main camera is turned off completely. Both chambers work at maximum mode, and the large one develops a thrust of 1700 kg, and small - 300 kg, so the total thrust is 2000 kg. The rest of the engines are similar in design.

The engines shown in Fig. 33 and 34 operate on self-igniting fuel. This fuel consists of hydrogen peroxide as the oxidizer and hydrazine hydrate as the fuel, in a weight ratio of 3:1. More precisely, the fuel is a complex composition consisting of hydrazine hydrate, methyl alcohol and copper salts as a catalyst that ensures a fast reaction (other catalysts are also used). The disadvantage of this fuel is that it causes corrosion of engine parts.

The weight of a single chamber engine is 160 kg, the specific gravity is

per kilogram of thrust. Engine length - 2.2 m. The pressure in the combustion chamber is about 20 ata. When operating at the minimum fuel supply to obtain the least thrust, which is 100 kg, the pressure in the combustion chamber decreases to 3 ata. The temperature in the combustion chamber reaches 2500 °C, the gas flow rate is about 2100 m/s. Fuel consumption is 8 kg/s, and the specific fuel consumption is 15.3 kg fuel per 1 kg thrust per hour.

Fig. 33. Single-chamber rocket engine for rocket aircraft

Fig. 34. Two-chamber aircraft rocket engine.

Fig. 35. Scheme of fuel supply in an aviation LRE.

The scheme of fuel supply to the engine is shown in Fig. 35. As in a rocket engine, the supply of fuel and oxidizer stored in separate tanks is carried out at a pressure of about 40 ata impeller driven pumps. A general view of the turbopump unit is shown in Fig. 36. The turbine runs on a steam-gas mixture, which, as before, is obtained as a result of the decomposition of hydrogen peroxide in a steam-gas generator, which in this case is filled with a solid catalyst. Before entering the combustion chamber, the fuel cools the walls of the nozzle and the combustion chamber, circulating in a special cooling jacket. The change in the fuel supply necessary to control the engine thrust during the flight is achieved by changing the supply of hydrogen peroxide to the steam-gas generator, which causes a change in the speed of the turbine. The maximum speed of the impeller is 17,200 rpm. The engine is started using an electric motor that drives the turbopump unit.

Fig. 36. Turbopump unit of an aviation rocket engine.

1 - gear drive from the starting electric motor; 2 - pump for the oxidizer; 3 - turbine; 4 - fuel pump; 5 - turbine exhaust pipe.

In FIG. 37 shows a diagram of the installation of a single-chamber rocket engine in the rear fuselage of one of the experimental rocket aircraft.

The purpose of aircraft with liquid-propellant engines is determined by the properties of liquid-propellant rocket engines - high thrust and, accordingly, high power at high flight speeds and high altitudes and low efficiency, i.e., high fuel consumption. Therefore, rocket engines are usually installed on military aircraft - interceptor fighters. The task of such an aircraft is to quickly take off and dial when receiving a signal about the approach of enemy aircraft. great height, on which these aircraft usually fly, and then, using their advantage in flight speed, impose on the enemy air battle. Total duration the flight time of a liquid-propellant aircraft is determined by the fuel capacity of the aircraft and is 10-15 minutes, so these aircraft can usually make combat operations only in the vicinity of their airport.

Fig. 37. Scheme of the installation of rocket engines on the plane.

Fig. 38. Rocket fighter (view in three projections)

In FIG. 38 shows an interceptor fighter with the LRE described above. The dimensions of this aircraft, like other aircraft of this type, are usually small. The total weight of the aircraft with fuel is 5100 kg; fuel reserve (over 2.5 tons) is only enough for 4.5 minutes of engine operation at full power. Max speed flight - over 950 km/h; the ceiling of the aircraft, i.e. the maximum height that it can reach, is 16,000 m. The rate of climb of an aircraft is characterized by the fact that in 1 minute it can rise from 6 to 12 km.

Fig. 39. The device of a rocket aircraft.

In FIG. 39 shows the device of another aircraft with a rocket engine; this is an experimental aircraft built to achieve flight speeds in excess of the speed of sound (i.e. 1200 km/h at the ground). On the plane, in the rear of the fuselage, an LRE is installed, which has four identical chambers with a total thrust of 2720 kg. Engine length 1400 mm, maximum diameter 480 mm, weight 100 kg. The stock of fuel on the plane, which is used as alcohol and liquid oxygen, is 2360 l.

Fig. 40. Four-chamber aircraft rocket engine.

The external view of this engine is shown in Fig. 40.

Other applications of LRE

Along with the main use of liquid-propellant rocket engines as engines for long-range missiles and rocket aircraft, they are currently used in a number of other cases.

LREs have been widely used as engines for heavy rocket projectiles, similar to the one shown in Fig. 41. The engine of this projectile can serve as an example of the simplest rocket engine. Fuel (gasoline and liquid oxygen) is supplied to the combustion chamber of this engine under the pressure of neutral gas (nitrogen). In FIG. 42 shows a diagram of a heavy rocket used as a powerful anti-aircraft projectile; the diagram shows the overall dimensions of the rocket.

Liquid-propellant rocket engines are also used as starting aircraft engines. In this case, a low-temperature hydrogen peroxide decomposition reaction is sometimes used, which is why such engines are called "cold".

There are cases of using LRE as boosters for aircraft, in particular, aircraft with turbojet engines. In this case, fuel supply pumps are sometimes driven from the turbojet engine shaft.

Liquid-propellant rocket engines are also used, along with powder engines, for launching and accelerating aircraft (or their models) with ramjet engines. As you know, these engines develop very high thrust at high flight speeds, high speeds of sound, but do not develop thrust at all during takeoff.

Finally, we should mention one more application of LRE, which takes place in recent times. To study the behavior of an aircraft at high flight speeds approaching and exceeding the speed of sound requires a serious and costly research work. In particular, it is required to determine the resistance of aircraft wings (profiles), which is usually carried out in special wind tunnels. In order to create in such pipes the conditions corresponding to the flight of an aircraft at high speed, it is necessary to have power plants of very high power to drive the fans that create a flow in the pipe. As a result, the construction and operation of tubes for testing at supersonic speeds require huge costs.

Recently, along with the construction of supersonic tubes, the task of studying various wing profiles of high-speed aircraft, as well as testing ramjet engines, by the way, is also being solved with the help of liquid-propellant

Fig. 41. Rocket projectile with rocket engine.

engines. According to one of these methods, the investigated profile is installed on a long-range rocket with a liquid-propellant rocket engine, similar to the one described above, and all readings of instruments that measure the resistance of the profile in flight are transmitted to the ground using radio telemetry devices.

Fig. 42. Scheme of the device of a powerful anti-aircraft projectile with a rocket engine.

7 - combat head; 2 - cylinder with compressed nitrogen; 3 - tank with oxidizer; 4 - fuel tank; 5 - liquid-propellant engine.

According to another method, a special rocket trolley is being built, moving along rails with the help of a liquid-propellant rocket engine. The results of testing a profile installed on such a trolley in a special weight mechanism are recorded by special automatic devices also located on the trolley. Such a rocket cart is shown in Fig. 43. The length of the rail track can reach 2–3 km.

Fig. 43. Rocket trolley for testing aircraft wing profiles.

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