Magnetoplasmadynamic thruster

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. 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. One potential application of magnetoplasmadynamic thrusters is the main propulsion engine for heavy cargo and piloted space vehicles (example engine a 2 {displaystyle a^{2}} for Manned mission to Mars). In theory, MPD thrusters could produce extremely high specific impulses (Isp) with an exhaust velocity of up to and beyond 110000 m/s, 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) (45 lbF ), 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. MPD thruster technology has been explored academically, but commercial interest has been low due to several remaining problems. One big problem is that power requirements on the order of hundreds of kilowatts are required for optimum performance. Current interplanetary spacecraft power systems (such as radioisotope thermoelectric generators and solar arrays) are incapable of producing that much power. NASA's Project Prometheus reactor was expected to generate power in the hundreds of kilowatts range but was discontinued in 2005. A project to produce a space-going nuclear reactor designed to generate 600 kilowatts of electrical power began in 1963 and ran for most of the 1960s in the USSR. It was to power a communication satellite which was in the end not approved. Nuclear reactors supplying kilowatts of electrical power (of the order of ten times more than current RTG power supplies) have been orbited by the USSR: RORSAT; and TOPAZ. Plans to develop a megawatt-scale nuclear reactor for the use aboard a manned spaceship were announced in 2009 by Russian nuclear Kurchatov Institute, national space agency Roskosmos, and confirmed by Russian President Dmitry Medvedev in his November 2009 address to the Federal Assembly.