Electric propulsion is a form of spacecraft propulsion used in outer space. Spacecraft propulsion is any method used to change the velocity of Spacecraft and artificial Satellites There are many different methods Outer space, often simply called space, comprises the relatively empty regions of the Universe outside the escape velocities of Celestial bodies. This type of rocket-like reaction engine utilize electric energy to obtain thrust from propellant carried with the vehicle. A reaction engine is an engine which provides propulsion by expelling Reaction mass, in accordance with Newton's third law of motion. Electric energy is the potential energy associated with the conservative Coulomb forces between Charged particles contained within a system, where Unlike rocket engines these kinds of engines do not necessarily have rocket nozzles, and thus many types are not considered true rockets. A rocket engine nozzle is a Propelling nozzle usually of the de Laval type used in a Rocket engine to expand and accelerate the Combustion A rocket engine is a Jet engine that uses only Propellant mass for forming its high speed propulsive jet.

While electric thrusters typically offer much higher specific impulse, due to electrical power constraints thrust is weaker compared to chemical thrusters by several orders of magnitude. Specific impulse (usually abbreviated I sp is a way to describe the efficiency of rocket and jet engines An order of magnitude is the class of scale or magnitude of any amount where each class contains values of a fixed ratio to the class preceding it ^[1]

The idea of electric propulsion dates back to 1906, when Robert Goddard considered the possibility in his personal notebook. Year 1906 ( MCMVI) was a Common year starting on Monday (link will display full calendar of the Gregorian calendar (or a Common year starting Robert Hutchings Goddard, PhD ( October 5, 1882 &ndash August 10 1945 U ^[2] Konstantin Tsiolkovsky published the idea in 1911. Year 1911 ( MCMXI) was a Common year starting on Sunday (link will display the full calendar of the Gregorian calendar (or a Common year

Contents 1 Types of electric propulsion 1.1 Electrostatic 1.2 Electrothermal 1.3 Electromagnetic 1.4 Other 2 Energy efficiency 3 See also 4 References 5 External links

Types of electric propulsion

The various technologies of electric propulsion for spacecraft are usually grouped in three families based on the type of force used to accelerate the ions of the plasma.

Electric propulsion systems can also be characterized in terms of their operation in either steady (continuous firing for a prescribed duration) or unsteady (pulsed firings accumulating to a desired thrust bit).

Electrostatic

If the acceleration is caused mainly by the Coulomb Force (i. ---- Bold text Coulomb's law', developed in the 1780s by French physicist Charles Augustin de Coulomb, may be stated in scalar form e application of a static electric field in the direction of the acceleration) the device is considered electrostatic. In Physics, the space surrounding an Electric charge or in the presence of a time-varying Magnetic field has a property called an electric field (that can

• Ion thruster
• Hall effect thruster
• Field Emission Electric Propulsion
• Colloid thruster

Electrothermal

The electrothermal category groups the devices where electromagnetic fields are used to generate a plasma to increase the heat of the bulk propellant. An ion thruster is a form of Electric propulsion used for Spacecraft propulsion that creates thrust by accelerating Ions Ion thrusters are characterized In Spacecraft propulsion, a Hall thruster is a type of Ion thruster in which the Propellant is accelerated by an electric field Field Emission Electric Propulsion ( FEEP) is an advanced electrostatic propulsion concept a form of Ion thruster, that uses liquid Metal (usually either A colloid thruster is a type of thruster which uses electrostatic acceleration of charged liquid droplets for propulsion In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature The thermal energy imparted to the propellant gas is then converted into kinetic energy by a nozzle of either physical material construction or by magnetic means. A nozzle is a mechanical device or Orifice designed to control the characteristics of a Fluid flow as it exits (or enters an enclosed chamber or Pipe. Low molecular weight gases are preferred propellants (e. g. hydrogen, helium, ammonia) for this kind of system.

Performance of electrothermal systems in terms of specific impulse (Isp) is somewhat modest (500 to ~1000 seconds), but exceeds that of cold gas thrusters, monopropellant thrusters, and even most bi-propellant thrusters. A cold gas thruster is a rocket engine/thruster that uses a (typically inert gas as the reaction mass In the USSR electrothermal engines were used since 1971, Soviet "Meteor-3", "Meteor-Priroda", "Resurs-O" satellite series and Russian "Elektro" satellite are equipped with them. The Union of Soviet Socialist Republics (USSR was a constitutionally Socialist state that existed in Eurasia from 1922 to 1991 The Union of Soviet Socialist Republics (USSR was a constitutionally Socialist state that existed in Eurasia from 1922 to 1991 Russia (Россия Rossiya) or the Russian Federation ( Rossiyskaya Federatsiya) is a transcontinental Country extending ^[3] Electrothermal systems by Aerojet (MR-510) are currently used on Lockheed-Martin A2100 satellites using hydrazine as a propellant. Aerojet is a major Rocket and missile propulsion manufacturer based primarily in Sacramento California with divisions in Redmond WA; Orange VA Lockheed Martin ( is a large multinational Aerospace manufacturer and advanced technology Company formed in 1995 by the merger of Hydrazine is a Chemical compound with the formula N2H4 It has an Ammonia -like odor and is derived from the same industrial chemistry

• DC arcjet
• microwave arcjet
• VASIMR

Electromagnetic

If the ions are accelerated either by the Lorentz Force or by the effect of an electromagnetic fields where the electric field is not in the direction of the acceleration, the device is considered electromagnetic. Arcjets are a form of Electric propulsion for Spacecraft, whereby an electrical discharge (arc is created in a flow of propellant (typically Hydrazine Arcjets are a form of Electric propulsion for Spacecraft, whereby an electrical discharge (arc is created in a flow of propellant (typically Hydrazine The Variable Specific Impulse Magnetoplasma Rocket ( VASIMR) is an electro-thermal thruster for Spacecraft propulsion. In Physics, the Lorentz force is the Force on a Point charge due to Electromagnetic fields It is given by the following equation

• MPD thruster
• Electrodeless plasma thruster
• Pulsed inductive thruster

Other

• Vacuum arc thruster

Energy efficiency

Further information: Reaction_engine#Energy_use

See also

• Battery electric vehicle

References

• Aerospace America, AIAA publication, December 2005, Propulsion and Energy section, pp. 54-55, written by Mitchell Walker.

External links

• Distributed Power Architecture for Electric Propulsion
• http://www.daviddarling.info/encyclopedia/E/electricprop.html
• http://www.nasa.gov/offices/oce/llis/0736.html

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