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A magnetoplasmadynamic (MPD) thruster (MPDT) is a form of electrically powered spacecraft propulsion which uses the Lorentz force (the force on a charged particle by an electromagnetic field) to generate thrust. It is sometimes referred to as Lorentz Force Accelerator (LFA) or (mostly in Japan) MPD arcjet. Generally, a gaseous material is ionized and fed into an acceleration chamber, where the magnetic and electrical fields are created using a power source. The particles are then propelled by the Lorentz force resulting from the interaction between the current flowing through the plasma and the magnetic field (which is either externally applied, or induced by the current) out through the exhaust chamber. Unlike chemical propulsion, there is no combustion of fuel. As with other electric propulsion variations, both specific impulse and thrust increase with power input, while thrust per watt drops. There are two main types of MPD thrusters, applied-field and self-field. Applied-field thrusters have magnetic rings surrounding the exhaust chamber to produce the magnetic field, while self-field thrusters have a cathode extending through the middle of the chamber. Applied fields are necessary at lower power levels, where self-field configurations are too weak. Various propellants such as xenon, neon, argon, hydrogen, hydrazine, and lithium have been used, with lithium generally being the best performer. According to Edgar Choueiri magnetoplasmadynamic thrusters have input power 100-500 kilowatts, exhaust velocity 15-60 kilometers per second, thrust 2.5-25 newtons and efficiency 40-60 percent.〔(Choueiri, Edgar Y. (2009). New dawn of electric rocket. Next-Generation Thruster )〕〔Choueiri, Edgar Y. (2009) (New dawn of electric rocket ) ''Scientific American'' 300, 58–65 〕 One potential application of magnetoplasmadynamic thrusters is the main propulsion engine for heavy cargo and piloted space vehicles (example engine for Manned mission to Mars).〔〔 == Advantages == In theory, MPD thrusters could produce extremely high specific impulses (Isp) with an exhaust velocity of up to and beyond , triple the value of current xenon-based ion thrusters, and about 25 times better than liquid rockets. MPD technology also has the potential for thrust levels of up to 200 newtons (N) (), by far the highest for any form of electric propulsion, and nearly as high as many interplanetary chemical rockets. This would allow use of electric propulsion on missions which require quick delta-v maneuvers (such as capturing into orbit around another planet), but with many times greater fuel efficiency.〔Kurchatov Institute with Roskosmos renewed the work over developing nuclear energy sources for interplanetary flights, June 2009, (in Russian〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「magnetoplasmadynamic thruster」の詳細全文を読む スポンサード リンク
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