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83-508: A jet engine is a type of reaction engine , discharging a fast-moving jet of heated gas (usually air) that generates thrust by jet propulsion . While this broad definition may include rocket , water jet , and hybrid propulsion, the term jet engine typically refers to an internal combustion air-breathing jet engine such as a turbojet , turbofan , ramjet , pulse jet , or scramjet . In general, jet engines are internal combustion engines . Air-breathing jet engines typically feature

166-419: A Δ v {\displaystyle \Delta v} of 9.8 m/s each second). If the possible rate is only g {\displaystyle g} or less, the maneuver can not be carried out at all with this engine. The power is given by where F {\displaystyle F} is the thrust and a {\displaystyle a} the acceleration due to it. Thus

249-478: A Δ v {\displaystyle \Delta v} of ca. 9.5 km/s (mostly for the speed to be acquired), but if the engine could produce Δ v {\displaystyle \Delta v} at a rate of only slightly more than g , it would be a slow launch requiring altogether a very large Δ v {\displaystyle \Delta v} (think of hovering without making any progress in speed or altitude, it would cost

332-417: A convergent-divergent nozzle is needed on high-speed aircraft. The engine thrust is highest if the static pressure of the gas reaches the ambient value as it leaves the nozzle. This only happens if the nozzle exit area is the correct value for the nozzle pressure ratio (npr). Since the npr changes with engine thrust setting and flight speed this is seldom the case. Also at supersonic speeds the divergent area

415-680: A rotating air compressor powered by a turbine , with the leftover power providing thrust through the propelling nozzle —this process is known as the Brayton thermodynamic cycle . Jet aircraft use such engines for long-distance travel. Early jet aircraft used turbojet engines that were relatively inefficient for subsonic flight. Most modern subsonic jet aircraft use more complex high-bypass turbofan engines . They give higher speed and greater fuel efficiency than piston and propeller aeroengines over long distances. A few air-breathing engines made for high-speed applications (ramjets and scramjets ) use

498-408: A compressor ( axial , centrifugal , or both), mixing fuel with the compressed air, burning the mixture in the combustor , and then passing the hot, high pressure air through a turbine and a nozzle . The compressor is powered by the turbine, which extracts energy from the expanding gas passing through it. The engine converts internal energy in the fuel to increased momentum of the gas flowing through

581-402: A computer. All reaction engines lose some energy, mostly as heat. Different reaction engines have different efficiencies and losses. For example, rocket engines can be up to 60–70% energy efficient in terms of accelerating the propellant. The rest is lost as heat and thermal radiation, primarily in the exhaust. Reaction engines are more energy efficient when they emit their reaction mass when

664-426: A computer. Some effects such as Oberth effect can only be significantly utilised by high thrust engines such as rockets; i.e., engines that can produce a high g-force (thrust per unit mass, equal to delta-v per unit time). In the ideal case m 1 {\displaystyle m_{1}} is useful payload and m 0 − m 1 {\displaystyle m_{0}-m_{1}}

747-426: A higher priority than fuel efficiency, fans tend to be smaller or absent. Because of these distinctions, turbofan engine designs are often categorized as low-bypass or high-bypass , depending upon the amount of air which bypasses the core of the engine. Low-bypass turbofans have a bypass ratio of around 2:1 or less. The term Advanced technology engine refers to the modern generation of jet engines. The principle

830-406: A jet of water. The mechanical arrangement may be a ducted propeller with nozzle, or a centrifugal compressor and nozzle. The pump-jet must be driven by a separate engine such as a Diesel or gas turbine . All jet engines are reaction engines that generate thrust by emitting a jet of fluid rearwards at relatively high speed. The forces on the inside of the engine needed to create this jet give

913-426: A large number of different types of jet engines, all of which achieve forward thrust from the principle of jet propulsion . Commonly aircraft are propelled by airbreathing jet engines. Most airbreathing jet engines that are in use are turbofan jet engines, which give good efficiency at speeds just below the speed of sound. A turbojet engine is a gas turbine engine that works by compressing air with an inlet and

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996-418: A mission, for example, when launching from or landing on a planet, the effects of gravitational attraction and any atmospheric drag must be overcome by using fuel. It is typical to combine the effects of these and other effects into an effective mission delta-v . For example, a launch mission to low Earth orbit requires about 9.3–10 km/s delta-v. These mission delta-vs are typically numerically integrated on

1079-418: A mission, for example, when launching from or landing on a planet, the effects of gravitational attraction and any atmospheric drag must be overcome by using fuel. It is typical to combine the effects of these and other effects into an effective mission delta-v . For example, a launch mission to low Earth orbit requires about 9.3–10 km/s delta-v. These mission delta-vs are typically numerically integrated on

1162-435: A particular engine design that if some bumps in a bypass duct are smoothed out the air will flow more smoothly giving a pressure loss reduction of x% and y% less fuel will be needed to get the take-off thrust, for example. This understanding comes under the engineering discipline Jet engine performance . How efficiency is affected by forward speed and by supplying energy to aircraft systems is mentioned later. The efficiency of

1245-759: A powerplant for the world's first jet- fighter aircraft , the Messerschmitt Me 262 (and later the world's first jet- bomber aircraft, the Arado Ar 234 ). A variety of reasons conspired to delay the engine's availability, causing the fighter to arrive too late to improve Germany's position in World War II , however this was the first jet engine to be used in service. Meanwhile, in Britain the Gloster E28/39 had its maiden flight on 15 May 1941 and

1328-413: A specific impulse that is both high and fixed such as Ion thrusters have exhaust velocities that can be enormously higher than this ideal, and thus end up powersource limited and give very low thrust. Where the vehicle performance is power limited, e.g. if solar power or nuclear power is used, then in the case of a large v e {\displaystyle v_{e}} the maximum acceleration

1411-429: A stationary engine does no useful work. Exhausting the entire usable propellant of a spacecraft through the engines in a straight line in free space would produce a net velocity change to the vehicle; this number is termed delta-v ( Δ v {\displaystyle \Delta v} ). If the exhaust velocity is constant then the total Δ v {\displaystyle \Delta v} of

1494-529: A strong thrust on the engine which pushes the craft forwards. Jet engines make their jet from propellant stored in tanks that are attached to the engine (as in a 'rocket') as well as in duct engines (those commonly used on aircraft) by ingesting an external fluid (very typically air) and expelling it at higher speed. A propelling nozzle produces a high velocity exhaust jet . Propelling nozzles turn internal and pressure energy into high velocity kinetic energy. The total pressure and temperature don't change through

1577-438: A substantial initial forward airspeed before it can function. Ramjets are considered the simplest type of air breathing jet engine because they have no moving parts in the engine proper, only in the accessories. Scramjets differ mainly in the fact that the air does not slow to subsonic speeds. Rather, they use supersonic combustion. They are efficient at even higher speed. Very few have been built or flown. The rocket engine uses

1660-419: A supersonic afterburning engine or 2200 K with afterburner lit. The pressure entering the nozzle may vary from 1.5 times the pressure outside the nozzle, for a single stage fan, to 30 times for the fastest manned aircraft at Mach 3+. Convergent nozzles are only able to accelerate the gas up to local sonic (Mach 1) conditions. To reach high flight speeds, even greater exhaust velocities are required, and so

1743-401: A test stand, sucks in fuel and generates thrust. How well it does this is judged by how much fuel it uses and what force is required to restrain it. This is a measure of its efficiency. If something deteriorates inside the engine (known as performance deterioration) it will be less efficient and this will show when the fuel produces less thrust. If a change is made to an internal part which allows

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1826-403: A thrust to weight ratio of more than one. To do this with the ion or more theoretical electrical drives, the engine would have to be supplied with one to several gigawatts of power, equivalent to a major metropolitan generating station . From the table it can be seen that this is clearly impractical with current power sources. Alternative approaches include some forms of laser propulsion , where

1909-461: A two-stage axial compressor feeding a single-sided centrifugal compressor . Practical axial compressors were made possible by ideas from A.A.Griffith in a seminal paper in 1926 ("An Aerodynamic Theory of Turbine Design"). Whittle would later concentrate on the simpler centrifugal compressor only. Whittle was unable to interest the government in his invention, and development continued at a slow pace. In Spain, pilot and engineer Virgilio Leret Ruiz

1992-476: A vehicle can be calculated using the rocket equation, where M is the mass of propellant, P is the mass of the payload (including the rocket structure), and v e {\displaystyle v_{e}} is the velocity of the rocket exhaust . This is known as the Tsiolkovsky rocket equation : For historical reasons, as discussed above, v e {\displaystyle v_{e}}

2075-480: Is Conclusions: These results apply for a fixed exhaust speed. Due to the Oberth effect and starting from a nonzero speed, the required potential energy needed from the propellant may be less than the increase in energy in the vehicle and payload. This can be the case when the reaction mass has a lower speed after being expelled than before – rockets are able to liberate some or all of the initial kinetic energy of

2158-627: Is achieved, the exhaust stops in space and has no kinetic energy; and the propulsive efficiency is 100% all the energy ends up in the vehicle (in principle such a drive would be 100% efficient, in practice there would be thermal losses from within the drive system and residual heat in the exhaust). However, in most cases this uses an impractical quantity of propellant, but is a useful theoretical consideration. Some drives (such as VASIMR or electrodeless plasma thruster ) actually can significantly vary their exhaust velocity. This can help reduce propellant usage and improve acceleration at different stages of

2241-422: Is approximately 3000 m/s, using a Hohmann transfer orbit . For the sake of argument, assume the following thrusters are options to be used: Observe that the more fuel-efficient engines can use far less fuel; their mass is almost negligible (relative to the mass of the payload and the engine itself) for some of the engines. However, these require a large total amount of energy. For Earth launch, engines require

2324-506: Is documented in the story of Ottoman soldier Lagâri Hasan Çelebi , who reportedly achieved flight using a cone-shaped rocket in 1633. The earliest attempts at airbreathing jet engines were hybrid designs in which an external power source first compressed air, which was then mixed with fuel and burned for jet thrust. The Italian Caproni Campini N.1 , and the Japanese Tsu-11 engine intended to power Ohka kamikaze planes towards

2407-418: Is for the ideal case again, with no energy lost on heat, etc. The latter causes a reduction of thrust, so it is a disadvantage even when the objective is to lose energy (deceleration). If the energy is produced by the mass itself, as in a chemical rocket, the fuel value has to be v e 2 / 2 {\displaystyle \scriptstyle {v_{\text{e}}^{2}/2}} , where for

2490-399: Is inversely proportional to it. Hence the time to reach a required delta-v is proportional to v e {\displaystyle v_{e}} . Thus the latter should not be too large. On the other hand, if the exhaust velocity can be made to vary so that at each instant it is equal and opposite to the vehicle velocity then the absolute minimum energy usage is achieved. When this

2573-578: Is less than required to give complete internal expansion to ambient pressure as a trade-off with external body drag. Whitford gives the F-16 as an example. Other underexpanded examples were the XB-70 and SR-71. The nozzle size, together with the area of the turbine nozzles, determines the operating pressure of the compressor. This overview highlights where energy losses occur in complete jet aircraft powerplants or engine installations. A jet engine at rest, as on

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2656-422: Is reaction mass (this corresponds to empty tanks having no mass, etc.). The energy required can simply be computed as This corresponds to the kinetic energy the expelled reaction mass would have at a speed equal to the exhaust speed. If the reaction mass had to be accelerated from zero speed to the exhaust speed, all energy produced would go into the reaction mass and nothing would be left for kinetic energy gain by

2739-519: Is recognised as containing the key features of a gas turbine. Barber's design included a chain-driven, reciprocating gas compressor , a combustion chamber , and a turbine. Barber's turbine was designed to burn producer gas obtained from wood, coal, oil, or other substances, heated in a retort or producer, from where the gases were conveyed into a receiver and cooled. Air and gas were then to be compressed in different cylinders and discharged into an "exploder" (combustion chamber) where they were ignited,

2822-445: Is roughly linear , and little reaction mass is needed. If Δ v {\displaystyle \Delta v} is comparable to v e , then there needs to be about twice as much fuel as combined payload and structure (which includes engines, fuel tanks, and so on). Beyond this, the growth is exponential; speeds much higher than the exhaust velocity require very high ratios of fuel mass to payload and structural mass. For

2905-439: Is sometimes written as where I sp {\displaystyle I_{\text{sp}}} is the specific impulse of the rocket, measured in seconds, and g 0 {\displaystyle g_{0}} is the gravitational acceleration at sea level. For a high delta-v mission, the majority of the spacecraft's mass needs to be reaction mass. Because a rocket must carry all of its reaction mass, most of

2988-443: Is that a turbine engine will function more efficiently if the various sets of turbines can revolve at their individual optimum speeds, instead of at the same speed. The true advanced technology engine has a triple spool, meaning that instead of having a single drive shaft, there are three, in order that the three sets of blades may revolve at different speeds. An interim state is a twin-spool engine, allowing only two different speeds for

3071-405: Is the exhaust velocity), which is simply the energy to accelerate the exhaust. Comparing the rocket equation (which shows how much energy ends up in the final vehicle) and the above equation (which shows the total energy required) shows that even with 100% engine efficiency, certainly not all energy supplied ends up in the vehicle – some of it, indeed usually most of it, ends up as kinetic energy of

3154-400: Is the propellant flow in kg/s, A e {\displaystyle A_{e}} is the cross-sectional area at the exit of the exhaust nozzle, and p {\displaystyle p} is the atmospheric pressure. Combined-cycle engines simultaneously use two or more different principles of jet propulsion. A water jet, or pump-jet, is a marine propulsion system that uses

3237-432: Is the specific energy of the rocket (potential plus kinetic energy) and Δ v {\displaystyle \Delta v} is a separate variable, not just the change in v {\displaystyle v} . In the case of using the rocket for deceleration; i.e., expelling reaction mass in the direction of the velocity, v {\displaystyle v} should be taken negative. The formula

3320-570: Is used for launching satellites, space exploration and crewed access, and permitted landing on the Moon in 1969. Rocket engines are used for high altitude flights, or anywhere where very high accelerations are needed since rocket engines themselves have a very high thrust-to-weight ratio . However, the high exhaust speed and the heavier, oxidizer-rich propellant results in far more propellant use than turbofans. Even so, at extremely high speeds they become energy-efficient. An approximate equation for

3403-903: The Gloster Meteor finally entered service with the RAF in July 1944. These were powered by turbojet engines from Power Jets Ltd., set up by Frank Whittle. The first two operational turbojet aircraft, the Messerschmitt Me 262 and then the Gloster Meteor entered service within three months of each other in 1944; the Me 262 in April and the Gloster Meteor in July. The Meteor only saw around 15 aircraft enter World War II action, while up to 1400 Me 262 were produced, with 300 entering combat, delivering

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3486-500: The aeolipile , a device described by Hero of Alexandria in 1st-century Egypt . This device directed steam power through two nozzles to cause a sphere to spin rapidly on its axis. It was seen as a curiosity. Meanwhile, practical applications of the turbine can be seen in the water wheel and the windmill . Historians have further traced the theoretical origin of the principles of jet engines to traditional Chinese firework and rocket propulsion systems. Such devices' use for flight

3569-663: The gasoline -fuelled HeS 3 of 5 kN (1,100 lbf), which was fitted to Heinkel's simple and compact He 178 airframe and flown by Erich Warsitz in the early morning of August 27, 1939, from Rostock -Marienehe aerodrome , an impressively short time for development. The He 178 was the world's first jet plane. Heinkel applied for a US patent covering the Aircraft Power Plant by Hans Joachim Pabst von Ohain on May 31, 1939; patent number US2256198, with M Hahn referenced as inventor. Von Ohain's design, an axial-flow engine, as opposed to Whittle's centrifugal flow engine,

3652-402: The ram effect of the vehicle's speed instead of a mechanical compressor. The thrust of a typical jetliner engine went from 5,000 lbf (22 kN) ( de Havilland Ghost turbojet) in the 1950s to 115,000 lbf (510 kN) ( General Electric GE90 turbofan) in the 1990s, and their reliability went from 40 in-flight shutdowns per 100,000 engine flight hours to less than 1 per 100,000 in

3735-400: The reaction mass does not provide the energy required to accelerate it, with the energy instead being provided from an external laser or other beam-powered propulsion system. Small models of some of these concepts have flown, although the engineering problems are complex and the ground-based power systems are not a solved problem. John Barber (engineer) John Barber (1734–1793)

3818-537: The 1950s, the jet engine was almost universal in combat aircraft, with the exception of cargo, liaison and other specialty types. By this point, some of the British designs were already cleared for civilian use, and had appeared on early models like the de Havilland Comet and Avro Canada Jetliner . By the 1960s, all large civilian aircraft were also jet powered, leaving the piston engine in low-cost niche roles such as cargo flights. The efficiency of turbojet engines

3901-518: The British embassy in Madrid a few years later by his wife, Carlota O'Neill , upon her release from prison. In 1935, Hans von Ohain started work on a similar design to Whittle's in Germany, both compressor and turbine being radial, on opposite sides of the same disc, initially unaware of Whittle's work. Von Ohain's first device was strictly experimental and could run only under external power, but he

3984-504: The French journalist Just Buisson  [ fr ; ro ] . For all reaction engines that carry on-board propellant (such as rocket engines and electric propulsion drives) some energy must go into accelerating the reaction mass. Every engine wastes some energy, but even assuming 100% efficiency, the engine needs energy amounting to (where M is the mass of propellent expended and V e {\displaystyle V_{e}}

4067-534: The Pratt & Whitney J57 and J75 models. There is also a derivative of the P&;W JT8D low-bypass turbofan that creates up to 35,000 horsepower (HP) . Jet engines are also sometimes developed into, or share certain components such as engine cores, with turboshaft and turboprop engines, which are forms of gas turbine engines that are typically used to power helicopters and some propeller-driven aircraft. There are

4150-400: The air/combustion gases to flow more smoothly the engine will be more efficient and use less fuel. A standard definition is used to assess how different things change engine efficiency and also to allow comparisons to be made between different engines. This definition is called specific fuel consumption , or how much fuel is needed to produce one unit of thrust. For example, it will be known for

4233-477: The combustor). The above pressure and temperature are shown on a Thermodynamic cycle diagram. Reaction engine Examples include jet engines , rocket engines , pump-jets , and more uncommon variations such as Hall effect thrusters , ion drives , mass drivers , and nuclear pulse propulsion . The discovery of the reaction engine has been attributed to the Romanian inventor Alexandru Ciurcu and to

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4316-404: The end of World War II were unsuccessful. Even before the start of World War II, engineers were beginning to realize that engines driving propellers were approaching limits due to issues related to propeller efficiency, which declined as blade tips approached the speed of sound . If aircraft performance were to increase beyond such a barrier, a different propulsion mechanism was necessary. This

4399-481: The energy produced by the fuel minus the energy gain of the reaction mass. The larger the speed of the rocket, the smaller the energy gain of the reaction mass; if the rocket speed is more than half of the exhaust speed the reaction mass even loses energy on being expelled, to the benefit of the energy gain of the rocket; the larger the speed of the rocket, the larger the energy loss of the reaction mass. We have where ϵ {\displaystyle \epsilon }

4482-407: The energy required is 50 MJ per kg reaction mass, only 20 MJ is used for the increase in speed of the reaction mass. The remaining 30 MJ is the increase of the kinetic energy of the rocket and payload. In general: Thus the specific energy gain of the rocket in any small time interval is the energy gain of the rocket including the remaining fuel, divided by its mass, where the energy gain is equal to

4565-425: The engine is controlled primarily by the operating conditions inside the engine which are the pressure produced by the compressor and the temperature of the combustion gases at the first set of rotating turbine blades. The pressure is the highest air pressure in the engine. The turbine rotor temperature is not the highest in the engine but is the highest at which energy transfer takes place ( higher temperatures occur in

4648-648: The engine, producing thrust. All the air entering the compressor is passed through the combustor, and turbine, unlike the turbofan engine described below. Turbofans differ from turbojets in that they have an additional fan at the front of the engine, which accelerates air in a duct bypassing the core gas turbine engine. Turbofans are the dominant engine type for medium and long-range airliners . Turbofans are usually more efficient than turbojets at subsonic speeds, but at high speeds their large frontal area generates more drag . Therefore, in supersonic flight, and in military and other aircraft where other considerations have

4731-495: The exhaust stream into furnaces for smelting ores . Given the technologies available to Barber, it is unlikely that a gas turbine could have been built that would have been able to create sufficient power to both compress the air and the gas and produce useful work. It wasn't until 1939, some 148 years after Barber's initial patent, that the first constant pressure gas turbine entered service in Neuchâtel, Switzerland . In

4814-423: The exhaust. If the specific impulse ( I s p {\displaystyle I_{sp}} ) is fixed, for a mission delta-v, there is a particular I s p {\displaystyle I_{sp}} that minimises the overall energy used by the rocket. This comes to an exhaust velocity of about ⅔ of the mission delta-v (see the energy computed from the rocket equation ). Drives with

4897-464: The first ground attacks and air combat victories of jet planes. Following the end of the war the German jet aircraft and jet engines were extensively studied by the victorious allies and contributed to work on early Soviet and US jet fighters. The legacy of the axial-flow engine is seen in the fact that practically all jet engines on fixed-wing aircraft have had some inspiration from this design. By

4980-400: The flight. However the best energetic performance and acceleration is still obtained when the exhaust velocity is close to the vehicle speed. Proposed ion and plasma drives usually have exhaust velocities enormously higher than that ideal (in the case of VASIMR the lowest quoted speed is around 15 km/s compared to a mission delta-v from high Earth orbit to Mars of about 4 km/s ). For

5063-712: The form of rocket engines they power model rocketry , spaceflight , and military missiles . Jet engines have propelled high speed cars, particularly drag racers , with the all-time record held by a rocket car . A turbofan powered car, ThrustSSC , currently holds the land speed record . Jet engine designs are frequently modified for non-aircraft applications, as industrial gas turbines or marine powerplants . These are used in electrical power generation, for powering water, natural gas, or oil pumps, and providing propulsion for ships and locomotives. Industrial gas turbines can create up to 50,000 shaft horsepower. Many of these engines are derived from older military turbojets such as

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5146-424: The fuel value also the mass of the oxidizer has to be taken into account. A typical value is v e {\displaystyle v_{\text{e}}} = 4.5 km/s, corresponding to a fuel value of 10.1   MJ/kg. The actual fuel value is higher, but much of the energy is lost as waste heat in the exhaust that the nozzle was unable to extract. The required energy E {\displaystyle E}

5229-599: The initially-expended reaction mass goes towards accelerating reaction mass rather than payload. If the rocket has a payload of mass P , the spacecraft needs to change its velocity by Δ v {\displaystyle \Delta v} , and the rocket engine has exhaust velocity v e , then the reaction mass M which is needed can be calculated using the rocket equation and the formula for I sp {\displaystyle I_{\text{sp}}} : For Δ v {\displaystyle \Delta v} much smaller than v e , this equation

5312-457: The late 1990s. This, combined with greatly decreased fuel consumption, permitted routine transatlantic flight by twin-engined airliners by the turn of the century, where previously a similar journey would have required multiple fuel stops. The principle of the jet engine is not new; however, the technical advances necessary to make the idea work did not come to fruition until the 20th century. A rudimentary demonstration of jet power dates back to

5395-421: The mixture of hot gas then being played against the vanes of a paddle wheel. Water was to be injected into the explosive mixture to cool the mouth of the chamber and, by producing steam, to increase the volume of the charge. The patent proposed various uses for the gas turbine including propulsion of ships, barges and boats by reaction , mechanical operations (grinding, rolling , forging etc.) and injection of

5478-394: The net thrust of a rocket engine is: Where F N {\displaystyle F_{N}} is the net thrust, I sp,vac {\displaystyle I_{\text{sp,vac}}} is the specific impulse , g 0 {\displaystyle g_{0}} is a standard gravity , m ˙ {\displaystyle {\dot {m}}}

5561-404: The nozzle but their static values drop as the gas speeds up. The velocity of the air entering the nozzle is low, about Mach 0.4, a prerequisite for minimizing pressure losses in the duct leading to the nozzle. The temperature entering the nozzle may be as low as sea level ambient for a fan nozzle in the cold air at cruise altitudes. It may be as high as the 1000 Kelvin exhaust gas temperature for

5644-424: The propellant. Also, for a given objective such as moving from one orbit to another, the required Δ v {\displaystyle \Delta v} may depend greatly on the rate at which the engine can produce Δ v {\displaystyle \Delta v} and maneuvers may even be impossible if that rate is too low. For example, a launch to Low Earth orbit (LEO) normally requires

5727-512: The rocket and payload. However, if the rocket already moves and accelerates (the reaction mass is expelled in the direction opposite to the direction in which the rocket moves) less kinetic energy is added to the reaction mass. To see this, if, for example, v e {\displaystyle v_{e}} =10 km/s and the speed of the rocket is 3 km/s, then the speed of a small amount of expended reaction mass changes from 3 km/s forwards to 7 km/s rearwards. Thus, although

5810-421: The same basic physical principles of thrust as a form of reaction engine , but is distinct from the jet engine in that it does not require atmospheric air to provide oxygen; the rocket carries all components of the reaction mass. However some definitions treat it as a form of jet propulsion . Because rockets do not breathe air, this allows them to operate at arbitrary altitudes and in space. This type of engine

5893-536: The state of the art in compressors. Alan Arnold Griffith published An Aerodynamic Theory of Turbine Design in 1926 leading to experimental work at the RAE . In 1928, RAF College Cranwell cadet Frank Whittle formally submitted his ideas for a turbojet to his superiors. In October 1929, he developed his ideas further. On 16 January 1930, in England, Whittle submitted his first patent (granted in 1932). The patent showed

5976-416: The theoretically possible thrust per unit power is 2 divided by the specific impulse in m/s. The thrust efficiency is the actual thrust as percentage of this. If, e.g., solar power is used, this restricts a {\displaystyle a} ; in the case of a large v e {\displaystyle v_{\text{e}}} the possible acceleration is inversely proportional to it, hence

6059-520: The time to reach a required delta-v is proportional to v e {\displaystyle v_{\text{e}}} ; with 100% efficiency: Examples: Thus v e {\displaystyle v_{\text{e}}} should not be too large. The power to thrust ratio is simply: Thus for any vehicle power P, the thrust that may be provided is: Suppose a 10,000 kg space probe will be sent to Mars. The required Δ v {\displaystyle \Delta v} from LEO

6142-431: The turbines. Ram compression jet engines are airbreathing engines similar to gas turbine engines in so far as they both use the Brayton cycle . Gas turbine and ram compression engines differ, however, in how they compress the incoming airflow. Whereas gas turbine engines use axial or centrifugal compressors to compress incoming air, ram engines rely only on air compressed in the inlet or diffuser. A ram engine thus requires

6225-401: The vehicle is travelling at high speed. This is because the useful mechanical energy generated is simply force times distance, and when a thrust force is generated while the vehicle moves, then: where F is the force and d is the distance moved. Dividing by length of time of motion we get: Hence: where P is the useful power and v is the speed. Hence, v should be as high as possible, and

6308-604: Was able to demonstrate the basic concept. Ohain was then introduced to Ernst Heinkel , one of the larger aircraft industrialists of the day, who immediately saw the promise of the design. Heinkel had recently purchased the Hirth engine company, and Ohain and his master machinist Max Hahn were set up there as a new division of the Hirth company. They had their first HeS 1 centrifugal engine running by September 1937. Unlike Whittle's design, Ohain used hydrogen as fuel, supplied under external pressure. Their subsequent designs culminated in

6391-663: Was an English coal viewer and inventor. He was born in Nottinghamshire , but moved to Warwickshire in the 1760s to manage collieries in the Nuneaton area. For a time he lived in Camp Hill House , between Hartshill and Nuneaton, and later lived in Attleborough . The same John Barber is thought to be the inventor named in several patents granted between 1766 and 1792. The most remarkable of these patents

6474-403: Was built in 1903 by Norwegian engineer Ægidius Elling . Such engines did not reach manufacture due to issues of safety, reliability, weight and, especially, sustained operation. The first patent for using a gas turbine to power an aircraft was filed in 1921 by Maxime Guillaume . His engine was an axial-flow turbojet, but was never constructed, as it would have required considerable advances over

6557-576: Was eventually adopted by most manufacturers by the 1950s. Austrian Anselm Franz of Junkers ' engine division ( Junkers Motoren or "Jumo") introduced the axial-flow compressor in their jet engine. Jumo was assigned the next engine number in the RLM 109-0xx numbering sequence for gas turbine aircraft powerplants, "004", and the result was the Jumo 004 engine. After many lesser technical difficulties were solved, mass production of this engine started in 1944 as

6640-472: Was for a gas turbine . Although nothing practical came out of this patent, Barber is recognised as the first person to describe the working principle of a constant pressure gas turbine . In 1791 Barber took out a patent (UK patent no. 1833 – Obtaining and Applying Motive Power, & c. A Method of Rising Inflammable Air for the Purposes of Procuring Motion, and Facilitating Metallurgical Operations ) which

6723-593: Was granted a patent for a jet engine design in March 1935. Republican president Manuel Azaña arranged for initial construction at the Hispano-Suiza aircraft factory in Madrid in 1936, but Leret was executed months later by Francoist Moroccan troops after unsuccessfully defending his seaplane base on the first days of the Spanish Civil War . His plans, hidden from Francoists, were secretly given to

6806-426: Was still rather worse than piston engines, but by the 1970s, with the advent of high-bypass turbofan jet engines (an innovation not foreseen by the early commentators such as Edgar Buckingham , at high speeds and high altitudes that seemed absurd to them), fuel efficiency was about the same as the best piston and propeller engines. Jet engines power jet aircraft , cruise missiles and unmanned aerial vehicles . In

6889-409: Was the motivation behind the development of the gas turbine engine, the most common form of jet engine. The key to a practical jet engine was the gas turbine , extracting power from the engine itself to drive the compressor . The gas turbine was not a new idea: the patent for a stationary turbine was granted to John Barber in England in 1791. The first gas turbine to successfully run self-sustaining

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