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Файл:Jet Propulsion Engine Fundamentals английский язык для студентов специальности «Проектирование авиационных и ракетных двигателей». Учебное пособие
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generating heat and creating reactive traction. Such engines with varying degrees of
success were refined, improved and improved, but their specific impulse remained
small anyway, that is, the design was inefficient and uneconomical. Soon, new types
of solid fuel appeared, allowing to obtain a greater specific impulse and develop more
thrust. Scientists of 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 40s, a prototype of modern
fuel was developed, which is used now.
Liquid rocket engines are an invention of K.E. Tsiolkovsky, who proposed them
as a power unit of a space rocket in 1903. In the 20s, work on the creation of rocket
engines began to be carried out in the United States, in the 30s - in the USSR. By the
beginning of World War II, the first experimental designs were created, and after its
end, liquid-propellant rocket engines 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 was launched. To launch it, a rocket
equipped with Russian Railways was used.
The device and principle of operation of chemical rocket engines. A solid-fuel
engine accommodates fuel and an oxidizing agent in its solid aggregate state, and the
container with fuel is also a combustion chamber. Fuel usually has the form of a core
with a central hole. In the process of oxidation, 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 a draft. This is the simplest design among all rocket engines.
In liquid RDs, fuel and oxidizing agent are in the liquid aggregate state in two
separate tanks. Through the feed channels they enter the combustion chamber, where
they are mixed and the combustion process occurs. The combustion products exit
through the nozzle, forming a draft. Liquid oxygen is usually used as an oxidizing
agent, and the fuel may be different: kerosene, liquid hydrogen, etc.
Pros and cons of chemical RD, their scope
The advantages of solid fuel RD are:
simplicity of construction;
comparative safety in terms of ecology;
low price;
reliability.
Disadvantages of solid propellant rocket motors:
time limit: fuel burns out very quickly;
the inability to restart the engine, stop it and regulate traction;
small specific gravity in the range of 2000-3000 m / s.
Analyzing the pros and cons of solid propellant rocket motors, we can conclude
that their use is justified only in those cases when you need a power unit of medium
power, quite cheap and easy to implement. The scope of their use is ballistic,
meteorological rockets, MANPADS, and also lateral space rocket boosters (they are
equipped with American rockets, they were not used in Soviet and Russian rockets).
Advantages of liquid taxiways:
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high specific impulse (about 4,500 m / s and higher);
the ability to control traction, stop and restart the engine;
less weight and compactness, which makes it possible to put into orbit even
large multi-ton loads.
The disadvantages of the rocket engine:
complex design and commissioning;
in zero gravity, liquids in tanks can move randomly. For their deposition,
additional energy sources must be used.
The scope of the rocket engine is mainly astronautics, since for military
purposes these engines are too expensive.
Despite the fact that so far the chemical taxiways are the only ones capable of
providing 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 large specific impulse.
Task 2. Decide if statements are true or false. Correct false statements.
1. Solid propellant rocket motors are used in those cases when you need a
power unit of low power, quite cheap and easy to implement.
2. Liquid oxygen is usually used as an oxidizing agent, and the fuel may be
different: kerosene, liquid hydrogen, etc.
3. The specific impulse value reflects the efficiency of the engine.
4. Rocket engines are strikingly different from each other not only by
design features, but also by the principle of operation.
5. The advantages of liquid fuel RD are: high specific impulse (about 4,500
m / s and higher); the ability to control traction, stop and restart the engine; no
additional energy sources must be used in zero gravity.
6. The first rocket engines used a powder that resembled gunpowder in
composition, the percentage of its components was the same.
7. In the second half of the 40s, a prototype of modern fuel was developed,
which is used now.
8. In a solid-fuel engine, the container with fuel is also a combustion
chamber and fuel usually has the form of a core with a central hole.
9. By the beginning of World War I, the first experimental designs were
created, and after its end, liquid-propellant rocket engines began to be massproduced.
10. A liquid RDs accommodates fuel and an oxidizing agent in its liquid
aggregate state, and the container with fuel is also a combustion chamber.
11. In liquid RDs, fuel and oxidizing agent enter the combustion chamber,
where they are mixed and the combustion process occurs.
12. The advantages of solid fuel RD are: simplicity of construction;
comparative safety in terms of ecology; time limit; reliability.
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Text 4
Task 1. Read and translate the text
Nuclear Rocket Engines (NRE)
This type of RD, unlike chemical ones, does not generate energy during fuel
combustion, but as a result of heating the working fluid with the energy of nuclear
reactions. NREs are isotopic, thermonuclear and nuclear.
History of creation. The design and operation of the NRE were developed back
in the 50s. Already in the 70s in the USSR and the USA, experimental samples were
ready, which were successfully tested. The solid-state Soviet RD-0410 engine with a
thrust of 3.6 tons was tested at the stand base, and the American NERVA reactor was
supposed to be installed on the Saturn V rocket before sponsorship of the lunar
program was stopped. In parallel, work was underway on the creation of gas-phase
NRE. Nowadays, scientific programs for the development of nuclear taxiways are
operating, experiments are being conducted at space stations.
Thus, there are already existing models of nuclear rocket engines, but so far
not one of them has been used outside laboratories or scientific bases. The potential
of such engines is quite high, but the risk associated with their use is also
considerable, so that so far they exist only in projects.
The device and principle of operation. Nuclear rocket engines are gas-, liquidand solid-phase depending on the state of aggregation of nuclear fuel. Fuel in solidphase NREs are fuel elements that are the same as in nuclear reactors. They are
located in the engine casing and in the process of decay of fissile material emit
thermal energy. The working fluid - gaseous hydrogen or ammonia - in contact with
the fuel rod absorbs energy and heats up, increasing in volume and contracting, and
then exits through the nozzle under high pressure.
The principle of operation of a liquid-phase NRE and its device is similar to
solid-phase, only the fuel is in a liquid state, which allows to increase the
temperature, and hence the thrust.
Gas-phase NRE operate on fuel in a gaseous state. Usually they use uranium.
Gaseous fuel can be held in the casing by an electric field or is located in a sealed
transparent bulb - a nuclear lamp. In the first case, the contact of the working fluid
with the fuel occurs, as well as a partial leakage of the latter, therefore, in addition to
the bulk of the fuel, the engine should have a reserve for periodic replenishment. In
the case of a nuclear lamp, no leakage occurs, and the fuel is completely isolated
from the flow of the working fluid.
Advantages and disadvantages of NRE. 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 - 14000 m / s, for gas-phase 30,000 m / s. However, their use entails contamination of the atmosphere with
radioactive emissions. Work is underway to create a safe, environmentally friendly
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and efficient nuclear engine, and the main "contender" for this role is a gas-phase
NRE with a nuclear lamp, where the radioactive substance is in a sealed flask and
does not come out with a reactive flame.
Task 2. Sum up the information given in the text.
Text 5
Task 1. Read and translate the text
Electric Rocket Engines (ERE)
Another potential competitor to chemical taxiways is electric taxiways,
powered by electric energy. ERE can be electrothermal, electrostatic, electromagnetic
or pulsed.
History of creation
The first ERE was designed in the 30s by the Soviet designer V.P. Glushko,
although the idea of creating such an engine appeared at the beginning of the
twentieth century. In the 60s, scientists from the USSR and the USA actively worked
on the creation of electric propulsion, and already in the 70s the first samples began
to be used in spacecraft as control engines.
Device and principle of operation
The electric propulsion system consists of the propulsion engine itself, the
structure of which depends on its type, supply systems for 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 are used as a working fluid, less often
hydrogen.
Electrostatic RDs are divided into colloidal, ionic and plasma. In them, charged
particles of the working fluid are accelerated due to 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 — the inert gas xenon —
passes through the annular anode and enters the gas discharge chamber with a
cathode-compensator. At high voltage between the anode and cathode, a spark flares
up, 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 the
electrons are brought out by the cathode-compensator.
Electromagnetic RDs have their own magnetic field - external or internal,
which accelerates the charged particles of the working fluid.
Pulse taxiways work due to the evaporation of solid fuel under the influence of
electric discharges.
Advantages and disadvantages of electric propulsion, scope of use
Among the advantages of electric propulsion:
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high specific impulse, the upper limit of which is practically unlimited;
low fuel consumption (working fluid).
Disadvantages:
high level of electricity consumption;
design complexity;
slight traction.
Today, the use of electric propulsion is limited to their installation on space
satellites, and solar panels are used as sources of electricity for them. At the same
time, it is these engines that can become the power plants that will make it possible to
explore space, therefore, work on the creation of their new models is actively carried
out in many countries. It is these power plants that most often were mentioned by
science fiction writers in their works on 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 can still
travel to the stars.
Text 6
Task 1. Read and translate the text
The Space Shuttle
When it comes (about infrequently, but still) about the most powerful rocket
engines, some people recall the American F-1, mounted on the Saturn-5, others about the Soviet RD-170, attached to the "Energy", and someone doesn’t remember
anything at all. Both Saturn and Energy are two super-heavy missiles, the first being
the leader in the payload, although the RD-170 is somewhat more powerful than the
F-1.
However, the Space Shuttle’s solid-fuel side accelerator engine leaves its
competitors far behind.
Brief anatomy of the Shuttle. Simplified, the entire system consists of 4
elements. The fuel tank contains fuel and an oxidizing agent for the operation of the
three main (marching) engines located in the lower part of the orbiter - the rocket
plane, in which the payload and crew are located. In addition to the spacecraft, two
accelerators are attached to the tank. The length of the Shuttle is 56 meters. At the
first start-up, the fuel tank was painted white, but in subsequent launches they did not
paint it.
So, it is the engine located in the side booster that is the most powerful ever
created, developing a thrust of 12.5 mega-newton. Engine thrust is expressed in
Newtons. If the engine produces 1 Newton, then it is able to give an object weighing
1 kg an acceleration of 1 m / s ^ 2.
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An acceleration of 1 m / s ^ 2 means that for every second the speed of the
object will increase by 1 m / s. That is, they took a liter bottle of water (it has a mass
of just 1 kg), fastened an engine to it, and after a second it will move at a speed of 1
m / s, next second 2 m / s, another second - 3 m / s and so on.
Thus, one booster is able to budge an object weighing 12,500 tons! And not
just to shift, but also to increase its speed by 1 m / s every second. Two boosters
already provide 25.5 mega-newton thrust.
126 flight of the Shuttle. Astronauts fly to repair the Hubble telescope. The
starting weight of the entire system is about 2000 tons. All this is easily lifted by two
accelerators. The contribution of orbiter marching engines to the total thrust at this
stage is insignificant - only about 5.3 mega-newton (~ 1.8 MN per engine).
5 engines (2 boosters + 3 on a rocket plane) in total at the start give out an
incredible 31 mega-newton thrust - this is even more than that of the 27-engine
Falcon Heavy. Moreover, more than 80% of the thrust is provided by the side
accelerator engines.
The combination in one system of liquid (own orbiter engines; on the gif in the
center), and solid fuel engines, creates some features of the launch. The spacecraft’s
engines are the first to start. And only when an answer is received about their regular
work, then the side boosters will turn on. This sequence proceeds from the
characteristics of solid-fuel engines - after ignition they cannot be turned off.
Despite such a powerful propulsion system, the Shuttle very seriously lost the
fifth “Saturn” and “Energy” in carrying capacity. The first threw into orbit as many as
140 tons (5 F-1 engines developed 33.5 MN of thrust at the start), the second - about
100 tons (4 RD-170 engines at the start gave 28.8 MN).
The Shuttle transported about 25 tons. In general, its carrying capacity was
about 90 tons. But these numbers also include the mass of the spacecraft - about 68
tons. The Shuttle, unlike the Energy-Buran, cannot fly without an orbiter, since it is
an integral part of the rocket. And ‘Energy’ could well have flown without Buran, as
it was a completely independent system.
Spent boosters were separated at an altitude of 45 kilometers and parachuted
down into the ocean, where they were selected by a special search group. Then they
were delivered to the manufacturer for repair for reuse.
Task 2. Answer the questions.
1. How many elements does the entire system of the Shuttle consist of?
2. Where are the payload and crew located?
3. What thrust does the engine develop?
4. What is the starting weight of the whole system?
5. How many accelerators are there in the Shuttle?
6. What provides more than 80% of the thrust?
7. What is the carrying capacity of the Shuttle?
8. Why is the Shuttle incapable of flying without an orbiter?
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9. What happened to spent boosters at an altitude of 45 kilometers?
Text 7
Task 1. Read and translate the text
Flight Testing
Flight testing of rocket propulsion systems is always conducted in
conjunction with tests of vehicles and other systems such as guidance, vehicle
controls, or ground support. These flights usually occur along missile and
space launch ranges, sometimes over the ocean. If a flight test vehicle
deviates from its intended path and appears to be headed for a populated area,
a range safety official (or a computer) will have to either cause a destruction
of the vehicle, abort the flight, or cause it to correct its course. Many
propulsion systems therefore include devices that will either terminate the
operation or trigger explosive devices that will cause the vehicle (and
therefore also the propulsion system) to disintegrate in flight.
Flight testing requires special launch support equipment, means for
observing, monitoring, and recording data (cameras, radar, telemetering, etc.),
equipment for assuring range safety and for reducing data and evaluating flight
test performance, and specially trained personnel. Different launch equipment is
needed for different kinds of vehicles. This includes launch tubes for shoulderheld infantry support missile launchers, movable turret-type mounted multiple
launchers installed on an army truck or a navy ship, a transporter for larger
missiles, and a track-propelled launch platform or fixed complex launch pads
for spacecraft launch vehicles. The launch equipment has to have provisions
for loading or placing the vehicle into a launch position, for allowing access
of various equipment and connections to launch support equipment (checkout,
monitoring, fueling, etc.), for aligning or aiming the vehicle, or for
withstanding the exposure to the hot rocket plume at launch.
During experimental flights extensive measurements are often made on
the behavior of the various vehicle subsystems; for example, rocket propulsion
parameters, such as chamber pressure, feed pressures, temperatures, and so on,
are measured and the data are telemetered and transmitted to a ground
receiving station for recording and monitoring. Some flight tests rely on
salvaging and examining the test vehicle.
Task 2. Describe the equipment for flight testing.
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Text 8
Task 1. Match the headings with the paragraph and title the text.
1. Turbojet Engines
2. Sounding Rockets
3. Rocket Engines
4. Jet Engines
5. Turbofan Engines
6. Turboprop Engines
1.______________. The term “jet engines” refers to any jet propulsion device
which utilizes air from the atmosphere together with the combustion of a fuel and
produces the jet for propulsion purposes.
The jet engine works on the principle of Newton’s Third Law of Motion. The
jet engine functions by taking air, compressing it, injecting fuel into the compressed
air and igniting the mixture which then expands through a turbine which drives the
compressor.
The standard fuel for jet engines is a kerosene-type fuel. Kerosene burns at a
hotter temperature than gasoline and it has a higher viscosity.
A typical jet fuel system consists of: fuel pump, fuel filter, fuel regulators,
shut-off valve, fuel manifold and discharge nozzles.
2. _______________. A turbojet derives its thrust by highly accelerating a
small mass of air, which goes through the engine. This engine consists of a diffuser, a
mechanical compressor, a combustion chamber, a mechanical turbine and an exhaust
nozzle.
The function of a diffuser is to transform the kinetic energy of the entering air
into a static pressure rise. The diffuser delivers its air to the mechanical compressor
which further compresses the air and delivers it to the combustion chamber. There
fuel nozzles feed fuel continuously, and continuous combustion takes place at
approximately constant pressure. The high temperature and high pressure gases then
enter the turbine, where they expand to provide power for the turbine.
The turbine is directly connected to the compressor, and all the power
developed by the turbine is absorbed by the compressor and the auxiliary apparatus.
The main function of the turbine is to provide power for the mechanical compressor.
After the gases leave the turbine, they expand further in the exhaust nozzle and are
ejected with a velocity greater than the flight-velocity to produce thrust for
propulsion.
Because of turbine material limitations, only a relatively small amount of fuel
can be burnt in the combustion chamber. The exhaust products downstream of the
turbine still contain a considerable amount of excess oxygen. Additional thrust can
therefore be obtained from the turbojet engine by providing an afterburner aft of the
turbine.
The turbine supplies the power that drives the compressor. The more the
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pressure of the air is raised by the compressor, the higher the efficiency of the engine.
Engines designed for the greatest economy have therefore tended towards higher
compression ratios. This has led to splitting the compressor and turbine into two
groups: a low-speed compressor driven by a low-speed turbine, and a separate highspeed compressor driven by a high-speed turbine, the two driving shafts being coaxial. This arrangement incorporates what is called a two-spool compressor.
3._________________. The turbofan engine combines features of both the
turbojet and turboprop engines. It has performance characteristics somewhere
between the other two engines.
The engine comprises a diffuser, a fan, a mechanical duct, and an exhaust
nozzle. The function of the diffuser is to convert the kinetic energy of the entering air
into a static pressure rise. The diffuser delivers its air to a fan which further
compresses it. Then the air flow is split and a portion enters the bypass duct. The
ratio of the airflow through the bypass duct to the air flow through the gas generator
is defined as the bypass ratio. The turbine provides the power for both the fan and the
compressor.
The exhaust gases are further expanded in the exhaust nozzle to a velocity
greater than the flight velocity, producing thrust for propulsion. The bypass air is also
expanded to a velocity higher than the flight velocity, producing additional thrust for
propulsion. Thus the turbofan engine derives its propulsive thrust from the high
velocity exhausts of both the bypass air and the gas generator gases.
The turbofan engine is somewhat more efficient than the turbojet at low
speeds. Compared with the turboprop it is lighter, less economical at low speeds and
more economical at high speeds. The turbofan engines are practically used for most
types of airplane installations, especially for transport type aircraft.
In the turbofan, also called the bypass engine, the exhaust gases actually are
expelled from the rear nozzle at a slower velocity than a turbojet engine. This
decreased velocity would provide less thrust. But the amount of air passing through a
turbofan engine is much larger than that passing through a turbojet, and results in a
much greater push. Though the turbofan engine takes in much greater quantities of
air, only about half of it is pumped into the combustion chamber, while the remainder
is ducted, actually with a lower fuel consumption, than the turbojet engine.
4. ________________. In principle, this engine is very similar to the turbojet
engine, differing only in that it uses a propeller to provide most of the propulsive
thrust.
The engine consists of a diffuser, a mechanical compressor, a combustion
chamber, a turbine, an exhaust nozzle, a reduction gear and a propeller. The diffuser,
mechanical compressor and combustion chamber function in the same manner as in
the turbojet engine. However, in the turboprop engine, the turbine extracts much
more power than it does in the turbojet engine, because the turbine provides power
for both the compressor and the propeller. When all of this energy is extracted from
the high temperature gases, there is little energy left for producing jet thrust. Thus,
the turboprop engine derives most of its propulsive thrust from the propeller and
derives only a small portion (10 to 25 % depending on the flight velocity) from the
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exhaust nozzle.
Since the shaft rotation speed of gas turbine engines is very high
(approximately 12,000 rpm), a reduction gear must be placed between the turbine
shaft and the propeller to operate efficiently. The turboprop engine is essentially a gas
turbine power plant because, as pointed out before, little power is derived from the
exhaust nozzle; still as flight speeds are increased, the ratio of nozzle power to
propeller power for maximum thrust tends to become higher. The propulsive thrust is
provided by a dual momentum change of the air. First, the propeller increases the air
momentum, and second, the over-all engine from diffuser to nozzle, provides an
internal momentum increase. The sum of these thrusts is the total thrust developed by
the engine.
Turboprop engines having two independently rotating turbines have proved
quite successful. One of the turbines drives the compressor, while the other drives the
propeller. The independent turbine has some advantages over the direct connected
type. Both the propeller and the compressor may operate at rotational speeds that
produce the best respective efficiencies. This allows the propeller to operate at high
speed during take-off and climb, thus reducing the tendency of the propeller to stall.
Propeller speed can be lowered at altitude, with a subsequent reduction in tip
compressibility losses.
5. ________________. A rocket is a jet-propulsion device, in which all the
propellants are burned rapidly at great pressure and release a large amount of energy.
The exhaust gas is guided rearward at great velocity and produces the reactive force
of propulsion.
In the rocket power plant all the propellants, as well as oxygen, which form the
propulsive jet are within the vehicle itself, while other engines get oxygen from the
atmosphere. Thus the rocket engine can be used in a vacuum and is able to provide a
possible means of propulsion for interplanetary vehicles.
Besides, it is suitable for high-flying, high-speed missiles and as a primary or
an auxiliary power plant of an aircraft.
Rocket engines are divided into two categories: solid and liquid.
The liquid-propellant rocket power plants can be started and stopped at will by
the remote operation of the propellant control valves. This cannot be done with solidpropellant systems, because when they have once started, the fuel in the combustion
chamber must continue to burn until it is exhausted.
Therefore the liquid-propellant rocket engines are used mostly for long
durations and the solid-propellant rocket power plants are intended for short flights.
Undoubtedly the simplest form of jet-propulsion power units is the rocket
engine, but the rate at which it consumes fuel has prevented its adoption as a power
plant for continuous operation over periods even as long as one hour.
The main reason for this is that, unlike other types of engine, the rocket does
not take the oxygen required to burn the fuel from its surroundings, but carries its
own supply. A hydrocarbon fuel, such as petrol, requires about 3.5 times its own
weight of oxygen to burn it completely; hence the weight of fuel that a rocketpropelled aircraft using fuel of this type would have to carry would be at least 4.5
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