Technology & Engineering
Jet Propulsion
Jet propulsion is a method of creating thrust by expelling a high-velocity jet of gas or fluid in the opposite direction of the desired movement. This principle is commonly used in aircraft and spacecraft propulsion systems. It relies on Newton's third law of motion, which states that for every action, there is an equal and opposite reaction.
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8 Key excerpts on "Jet Propulsion"
eBook - PDF- Paul G. A. Cizmas(Author)
- 2021(Publication Date)
- Cambridge University Press(Publisher)
Part I Basic Fluid Mechanics and Thermodynamics for Propulsion 1 Jet Propulsion Principle 1.1 Introduction 3 1.2 Propulsion Systems Classification 3 1.3 Brief History of Jet Propulsion 5 1.4 Jet Propulsion Principle 11 1.1 Introduction This introductory chapter starts with a classification of propulsion systems. This allows us to get familiar with some of the nomenclature used in this text. A brief history of Jet Propulsion is presented in order to understand the evolution of propulsion systems. The Jet Propulsion principle is then presented, and the expression of jet engine thrust is introduced using elementary arguments. A rigorous derivation of the thrust expression will be presented in Chapter 6. 1.2 Propulsion Systems Classification Propulsion, according to the Merriam-Webster Dictionary, is the action or process of driving a body forward or onward. A propulsion system is the device that accomplishes this task. The force generated by the propulsion system that produces the locomotion is called thrust. There are numerous ways to classify propulsion systems because there are numerous criteria that can be used. One option is to classify propulsion systems based on the means used for thrust generation. Several options are possible for thrust generation: jet, propeller, fan, and combinations of these, as shown in Table 1.1. The entire thrust generated by turbojet and ramjet engines is produced by the jet. In a turboprop engine, most of the thrust is generated by the propeller and a small fraction by the jet. In a turbofan engine, most of the thrust is generated by the fan and a small fraction by the jet. The entire thrust generated by the piston engine used on airplanes is produced by the propeller. A second way of classifying propulsion systems is based on the source of energy used to produce the thrust. The most common source of energy used by today’s propulsion systems is chemical energy.
eBook - ePub- George P. Sutton, Oscar Biblarz(Authors)
- 2016(Publication Date)
- Wiley(Publisher)
CHAPTER 1 CLASSIFICATION In general terms, propulsion is the act of changing the motion of a body with respect to an inertial reference frame. Propulsion systems provide forces that either move bodies initially at rest or change their velocity or that overcome retarding forces when bodies are propelled through a viscous medium. The word propulsion comes from the Latin propulsus, which is the past participle of the verb propellere, meaning “to drive away.” Jet Propulsion is a type of motion whereby a reaction force is imparted to a vehicle by the momentum of ejected matter. Rocket propulsion is a class of Jet Propulsion that produces thrust by ejecting matter, called the working fluid or propellant, stored entirely in the flying vehicle. Duct propulsion is another class of Jet Propulsion and it includes turbojets and ramjets; these engines are more commonly called air‐breathing engines. Duct propulsion devices mostly utilize their surrounding medium as the propellant, energized by its combustion with the vehicle's stored fuel. Combinations of rockets and duct propulsion devices have been attractive for some applications, and one is briefly described in this chapter. The energy source most commonly used in rocket propulsion is chemical combustion. Energy can also be supplied by solar radiation and by a nuclear reactor. Accordingly, the various propulsion devices in use can be divided into chemical propulsion, nuclear propulsion, and solar propulsion. Table 1–1 lists many important propulsion concepts according to their energy source and type of propellant. Radiant energy may originate from sources other than the sun and theoretically includes the transmission of energy by ground‐based microwaves and laser beams. Nuclear energy originates in transformations of mass within atomic nuclei and is generated by either fission or fusion. Energy sources are central to rocket performance and several kinds, both within and external to the vehicle, have been investigated
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Library Press(Publisher)
Requir es liquid hydrogen fuel which has very low density and requires heavily insulated tankage. Water jet A water jet, or pump jet, is a marine propulsion system that utilizes a jet of water. The mechanical arrangement may be a ducted propeller with nozzle, or a centrifugal compressor and nozzle. A pump jet schematic ____________________ WORLD TECHNOLOGIES ____________________ Type Description Advantages Disadvantages Water jet For propelling water rockets and jetboats; squirts water out the back through a nozzle In boats, can run in shallow water, high acceleration, no risk of engine overload (unlike propellers), less noise and vibration, highly maneuverable at all boat speeds, high speed efficiency, less vulnerable to damage from debris, very reliable, more load flexibility, less harmful to wildlife Can be less efficient than a propeller at low speed, more expensive, higher weight in boat due to entrained water, will not perform well if boat is heavier than the jet is sized for General physical principles 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 a strong thrust on the engine which pushes the craft forwards. Jet engines make their jet from propellant from tankage that is 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. Thrust Thrust from airbreathing jet engines depends on the difference in speed of the air before and after it goes through the jet engine, the 'master cross-section' A, and the density of the air p ____________________ WORLD TECHNOLOGIES ____________________ The motion impulse of the engine is equal to the fluid mass multiplied by the speed at which the engine emits this mass: I = mc where m is the fluid mass per second and c is the exhaust speed.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- White Word Publications(Publisher)
The effect of the nozzle is to dramatically accelerate the mass, converting most of the thermal energy into kinetic energy. Exhaust speed reaching as high as 10 times the speed of sound at sea level are common. Rocket engines provide essentially the highest specific powers and high specific thrusts of any engine used for spacecraft propulsion. Ion propulsion rockets can heat a plasma or charged gas inside a magnetic bottle and release it via a magnetic nozzle, so that no solid matter need come in contact with the plasma. Of course, the machinery to do this is complex, but research into nuclear fusion has developed methods, some of which have been proposed to be used in propulsion systems, and some have been tested in a lab. Electromagnetic propulsion ____________________ WORLD TECHNOLOGIES ____________________ This test engine accelerates ions using electrostatic forces Rather than relying on high temperature and fluid dynamics to accelerate the reaction mass to high speeds, there are a variety of methods that use electrostatic or electromagnetic forces to accelerate the reaction mass directly. Usually the reaction mass is a stream of ions. Such an engine typically uses electric power, first to ionize atoms, and then to create a voltage gradient to accelerate the ions to high exhaust velocities. The idea of electric propulsion dates back to 1906, when Robert Goddard considered the possibility in his personal notebook. Konstantin Tsiolkovsky published the idea in 1911. For these drives, at the highest exhaust speeds, energetic efficiency and thrust are all inversely proportional to exhaust velocity. Their very high exhaust velocity means they require huge amounts of energy and thus with practical power sources provide low thrust, but use hardly any fuel.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- The English Press(Publisher)
The effect of the nozzle is to dramatically accelerate the mass, converting most of the thermal energy into kinetic energy. Exhaust speed reaching as high as 10 times the speed of sound at sea level are common. Rocket engines provide essentially the highest specific powers and high specific thrusts of any engine used for spacecraft propulsion. Ion propulsion rockets can heat a plasma or charged gas inside a magnetic bottle and release it via a magnetic nozzle, so that no solid matter need come in contact with the plasma. Of course, the machinery to do this is complex, but research into nuclear fusion has developed methods, some of which have been proposed to be used in propulsion systems, and some have been tested in a lab. ________________________ WORLD TECHNOLOGIES ________________________ Electromagnetic propulsion This test engine accelerates ions using electrostatic forces Rather than relying on high temperature and fluid dynamics to accelerate the reaction mass to high speeds, there are a variety of methods that use electrostatic or electro-magnetic forces to accelerate the reaction mass directly. Usually the reaction mass is a stream of ions. Such an engine typically uses electric power, first to ionize atoms, and then to create a voltage gradient to accelerate the ions to high exhaust velocities. The idea of electric propulsion dates back to 1906, when Robert Goddard considered the possibility in his personal notebook. Konstantin Tsiolkovsky published the idea in 1911. For these drives, at the highest exhaust speeds, energetic efficiency and thrust are all inversely proportional to exhaust velocity. Their very high exhaust velocity means they require huge amounts of energy and thus with practical power sources provide low thrust, but use hardly any fuel. For some missions, particularly reasonably close to the Sun, solar energy may be sufficient, and has very often been used, but for others further out or at higher power,
No longer available |Learn more- (Author)
- 2014(Publication Date)
- College Publishing House(Publisher)
The effect of the nozzle is to dramatically accelerate the mass, converting most of the thermal energy into kinetic energy. Exhaust speed reaching as high as 10 times the speed of sound at sea level are common. Rocket engines provide essentially the highest specific powers and high specific thrusts of any engine used for spacecraft propulsion. Ion propulsion rockets can heat a plasma or charged gas inside a magnetic bottle and release it via a magnetic nozzle, so that no solid matter need come in contact with the plasma. Of course, the machinery to do this is complex, but research into nuclear fusion has developed methods, some of which have been proposed to be used in propulsion systems, and some have been tested in a lab. ________________________ WORLD TECHNOLOGIES ________________________ Electromagnetic propulsion This test engine accelerates ions using electrostatic forces Rather than relying on high temperature and fluid dynamics to accelerate the reaction mass to high speeds, there are a variety of methods that use electrostatic or electromagnetic forces to accelerate the reaction mass directly. Usually the reaction mass is a stream of ions. Such an engine typically uses electric power, first to ionize atoms, and then to create a voltage gradient to accelerate the ions to high exhaust velocities. The idea of electric propulsion dates back to 1906, when Robert Goddard considered the possibility in his personal notebook. Konstantin Tsiolkovsky published the idea in 1911. For these drives, at the highest exhaust speeds, energetic efficiency and thrust are all inversely proportional to exhaust velocity. Their very high exhaust velocity means they require huge amounts of energy and thus with practical power sources provide low thrust, but use hardly any fuel. For some missions, particularly reasonably close to the Sun, solar energy may be sufficient, and has very often been used, but for others further out or at higher power,
eBook - PDF- Thawar T. Arif(Author)
- 2010(Publication Date)
- IntechOpen(Publisher)
12 Low-thrust Propulsion Technologies, Mission Design, and Application John W. Dankanich Gray Research Inc. U.S.A. 1. Introduction Electric propulsion has been widely accepted for station-keeping and final orbit insertion of commercial satellites. NASA, JAXA, and ESA have all used primary electric propulsion systems for science missions. Electric propulsion systems have been recently developed with a significant increase in performance and ability to process large amounts of onboard solar power. While the use of electric propulsion offers significant performance gains, it is not appropriate for all missions, has limitations, and the trajectories have characteristics that may be counterintuitive to those unfamiliar with low-thrust trajectory design. This chapter describes recent U.S. technology investments in electric propulsion thrusters with emphasis on mission application and low-thrust mission design for interplanetary trajectories and geosynchronous transfer using primary electric propulsion. 2. Overview of electric propulsion technologies Unlike chemical propulsion, which is limited to the energy available through the decomposition or combustion of molecular compounds, electric propulsion makes use of energy from an external source, typically solar power, to electrically accelerate the propellant to higher energies. The efficiency of momentum transfer is often described in terms of specific impulse which is proportional to the average exhaust velocity in the thrust direction. ܫ ௦ ൌ ݒ ா ௫௨௦௧ ݃ (1) The three basic types of electric propulsion systems are electrothermal, electrostatic, and electromagnetic. The types are categorized by the method of accelerating the propellant. Resistojets, arcjets, pulsed plasma, gridded-ion and Hall thrusters have significant flight experience. Electrothermal thrusters are the most widely used electric propulsion systems to date, but electrostatic systems are the industry’s state-of-the-art (SOA) with higher specific impulses.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Orange Apple(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 2 Rocket Engine RS-68 being tested at NASA's Stennis Space Center. The nearly transparent exhaust is due to this engine's exhaust being mostly superheated steam (water vapor from its propellants, hydrogen and oxygen) ________________________ WORLD TECHNOLOGIES ________________________ Viking 5C rocket engine A rocket engine , or simply rocket, is a jet engine that uses only propellant mass for forming its high speed propulsive jet. Rocket engines are reaction engines and obtain thrust in accordance with Newton's third law. Since they need no external material to form their jet, rocket engines can be used for spacecraft propulsion as well as terrestrial uses, such as missiles. Most rocket engines are internal combustion engines, although non combusting forms also exist. Rocket engines as a group have the highest exhaust velocities, are by far the lightest, and are the least energy efficient of all types of jet engines. ________________________ WORLD TECHNOLOGIES ________________________ Terminology Chemical rockets are rockets powered by exothermic chemical reactions of the propellant. Rocket motor (or solid-propellant rocket motor ) is a synonymous term with rocket engine that usually refers to solid rocket engines. Liquid rockets (or liquid-propellant rocket engine ) use one or more liquid propellants that are held in tanks prior to burning. Hybrid rockets have a solid propellant in the combustion chamber and a second liquid or gas propellant is added to permit it to burn. Thermal rockets are rockets where the propellant is inert, but is heated by a power source such as solar or nuclear power or beamed energy. Principle of operation How rocket engines work
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