Editing Ion thruster (section)

== Electromagnetic thrusters ==
{{main|Plasma propulsion engine}}
{{Self-contradictory|section=about=electromagnetic thrusters|article=Electrically powered spacecraft propulsion|date=April 2018}}

=== Pulsed inductive thrusters ===
{{main|Pulsed inductive thruster}}

[[Pulsed inductive thruster]]s (PITs) use pulses instead of continuous thrust and have the ability to run on power levels on the order of megawatts (MW). PITs consist of a large [[electromagnetic coil|coil]] encircling a cone shaped tube that emits the propellant gas. [[Ammonia]] is the gas most commonly used. For each pulse, a large charge builds up in a group of capacitors behind the coil and is then released. This creates a current that moves circularly in the direction of jθ. The current then creates a magnetic field in the outward radial direction (Br), which then creates a current in the gas that has just been released in the opposite direction of the original current. This opposite current ionizes the ammonia. The positively charged ions are accelerated away from the engine due to the electric field jθ crossing the magnetic field Br, due to the Lorentz force.<ref>{{cite web|url=http://gltrs.grc.nasa.gov/reports/2003/CR-2003-212714.pdf|title=Pulsed Inductive Thruster (PIT): Modeling and Validation Using the MACH2 Code |access-date=2007-11-21|first=Pavlos G.|last=Mikellides|url-status=dead|archive-url=https://web.archive.org/web/20061010033732/http://gltrs.grc.nasa.gov/reports/2003/CR-2003-212714.pdf|archive-date=2006-10-10}} {{PD-notice}}</ref>

=== Magnetoplasmadynamic thruster ===
{{main|Magnetoplasmadynamic thruster}}

[[Magnetoplasmadynamic thruster|Magnetoplasmadynamic]] (MPD) thrusters and [[lithium Lorentz force accelerator]] (LiLFA) thrusters use roughly the same idea. The LiLFA thruster builds on the MPD thruster. [[Hydrogen]], [[argon]], [[ammonia]] and [[nitrogen]] can be used as propellant. In a certain configuration, the ambient gas in [[low Earth orbit]] (LEO) can be used as a propellant. The gas enters the main chamber where it is ionized into [[Plasma (physics)|plasma]] by the electric field between the [[anode]] and the [[cathode]]. This plasma then conducts electricity between the anode and the cathode, closing the circuit. This new current creates a magnetic field around the cathode, which crosses with the electric field, thereby accelerating the plasma due to the Lorentz force.

The LiLFA thruster uses the same general idea as the MPD thruster, though with two main differences. First, the LiLFA uses lithium vapor, which can be stored as a solid. The other difference is that the single cathode is replaced by multiple, smaller cathode rods packed into a [[Hollow cathode effect|hollow cathode]] tube. MPD cathodes are easily corroded due to constant contact with the plasma. In the LiLFA thruster, the lithium vapor is injected into the hollow cathode and is not ionized to its plasma form/corrode the cathode rods until it exits the tube. The plasma is then accelerated using the same [[Lorentz force]].<ref name="Sankaran">{{cite journal|url=https://massless.info/images/sankaran-icnta-2003.pdf |archive-url=https://web.archive.org/web/20221010091830/https://massless.info/images/sankaran-icnta-2003.pdf |archive-date=2022-10-10 |url-status=live|title=A Survey of Propulsion Options for Cargo and Piloted Missions to Mars|access-date=2016-10-18|first1=K. |last1=Sankaran|first2=L.|last2=Cassady|first3=A.D.|last3=Kodys|first4=E.Y.|last4=Choueiri|journal=Annals of the New York Academy of Sciences|year=2004|volume=1017|issue=1|pages=450–467|doi=10.1196/annals.1311.027 |pmid=15220162|bibcode=2004NYASA1017..450S|s2cid=1405279}}</ref><ref>{{cite web|url=http://gltrs.grc.nasa.gov/reports/2001/CR-2001-211114.pdf|title=High Power MPD Thruster Development at the NASA Glenn Research Center|access-date=2007-11-21|first1=Michael R.|last1=LaPointe|first2=Pavlos G.|last2=Mikellides|url-status=dead|archive-url=https://web.archive.org/web/20061011063710/http://gltrs.grc.nasa.gov/reports/2001/CR-2001-211114.pdf |archive-date=October 11, 2006}} {{PD-notice}}</ref><ref>{{cite web|url=http://dspace.mit.edu/bitstream/handle/1721.1/31061/33887503.pdf?sequence=1|title=Utilization of Ambient Gas as a Propellant for Low Earth Orbit Electric Propulsion|date=May 22, 1999|first=Buford Ray|last=Conley|url-status=dead|archive-url=https://web.archive.org/web/20110629174257/http://dspace.mit.edu/bitstream/handle/1721.1/31061/33887503.pdf?sequence=1|archive-date=June 29, 2011}}</ref>

In 2013, Russian company the [[Chemical Automatics Design Bureau]] successfully conducted a bench test of their MPD engine for long-distance space travel.<ref>{{cite web |date=17 December 2013 |title="В Воронеже создали двигатель для Марса" в блоге "Перспективные разработки, НИОКРы, изобретения" - Сделано у нас |url=http://sdelanounas.ru/blogs/44948 |publisher=Сделано у нас |language=ru}}</ref>

=== Electrodeless plasma thrusters ===
{{main|Electrodeless plasma thruster}}

[[Electrodeless plasma thruster]]s have two unique features: the removal of the anode and cathode electrodes and the ability to throttle the engine. The removal of the electrodes eliminates erosion, which limits lifetime on other ion engines. Neutral gas is first ionized by [[electromagnetic radiation|electromagnetic waves]] and then transferred to another chamber where it is accelerated by an oscillating electric and magnetic field, also known as the [[ponderomotive force]]. This separation of the ionization and acceleration stages allows throttling of propellant flow, which then changes the thrust magnitude and specific impulse values.<ref>{{cite web|url=http://www.elwingcorp.com/files/IEPC05-article.pdf|title=Development of a High Power Electrodeless Thruster|access-date=2007-11-21|first=Gregory D.|last=Emsellem |archive-url=https://web.archive.org/web/20080515145645/http://www.elwingcorp.com/files/IEPC05-article.pdf|archive-date=2008-05-15|url-status=dead}}</ref>

=== Helicon double layer thrusters ===
{{main|Helicon double-layer thruster}}

A helicon double layer thruster is a type of plasma thruster that ejects high velocity [[ionized]] gas to provide [[thrust]]. In this design, gas is injected into a tubular chamber (the ''source tube'') with one open end. [[Radio frequency]] AC power (at [[ISM band|13.56 MHz]] in the prototype design) is coupled into a specially shaped [[antenna (radio)|antenna]] wrapped around the chamber. The [[electromagnetic wave]] emitted by the antenna causes the gas to break down and form a plasma. The antenna then excites a [[helicon (physics)|helicon wave]] in the plasma, which further heats it. The device has a roughly constant [[magnetic field]] in the source tube (supplied by [[solenoid]]s in the prototype), but the magnetic field diverges and rapidly decreases in magnitude away from the source region and might be thought of as a kind of magnetic [[nozzle]]. In operation, a sharp boundary separates the high density plasma inside the source region and the low density plasma in the exhaust, which is associated with a sharp change in electrical potential. Plasma properties change rapidly across this boundary, which is known as a ''current-free electric [[double layer (plasma)|double layer]]''. The electrical potential is much higher inside the source region than in the exhaust and this serves both to confine most of the electrons and to accelerate the ions away from the source region. Enough electrons escape the source region to ensure that the plasma in the exhaust is neutral overall.

=== Variable Specific Impulse Magnetoplasma Rocket (VASIMR) ===
{{main|Variable Specific Impulse Magnetoplasma Rocket}}

The proposed [[Variable Specific Impulse Magnetoplasma Rocket]] (VASIMR) functions by using [[radio waves]] to ionize a [[propellant]] into a plasma, and then using a [[magnetic field]] to accelerate the plasma out of the back of the [[rocket engine]] to generate thrust. The VASIMR is currently being developed by [[Ad Astra Rocket Company]], headquartered in [[Houston]], [[Texas]], with help from [[Canada]]-based [[Nautel]], producing the 200&nbsp;kW RF generators for ionizing propellant. Some of the components and "plasma shoots" experiments are tested in a laboratory settled in [[Liberia, Costa Rica]]. This project is led by former NASA astronaut [[Franklin Chang-Díaz]] (CRC-USA). A 200&nbsp;kW VASIMR test engine was in discussion to be fitted in the exterior of the [[International Space Station]], as part of the plan to test the VASIMR in space; however, plans for this test onboard ISS were canceled in 2015 by [[NASA]], with a free flying VASIMR test being discussed by Ad Astra instead.<ref name="VASiMRscrapped"/> An envisioned 200&nbsp;MW engine could reduce the duration of flight from Earth to Jupiter or Saturn from six years to fourteen months, and Mars from 7 months to 39 days.<ref>{{cite web|last=Zyga|first=Lisa|date=2009|title=Plasma Rocket Could Travel to Mars in 39 Days|url=http://phys.org/news174031552.html|work=[[Phys.org]]}}</ref>

=== Microwave electrothermal thrusters ===
{{multiple image
 | align         = right
 | header        = [[Microwave electrothermal thruster]]
 | caption_align = center
 | header_align  = center
 | total_width   = 500

 | image1   = MET Sketch 1.jpg
 | width1   = 1221
 | height1  = 629
 | alt1     = Thruster components
 | caption1 = <small style="font-size:90%;">Thruster components</small>

 | image2   = MET Sketch 2.jpg
 | width2   = 1233
 | height2  = 1297 
 | alt2     = Discharge Chamber
 | caption2 = <small style="font-size:90%;">Discharge chamber</small>
 }}

Under a research grant from the [[Glenn Research Center|NASA Lewis Research Center]] during the 1980s and 1990s, Martin C. Hawley and Jes Asmussen led a team of engineers in developing a microwave electrothermal thruster (MET).<ref>{{cite news|title=Less Fuel, More Thrust: New Engines are Being Designed for Deep Space|newspaper=The Arugus-Press|location=Owosso, Michigan|page=10|volume=128|number=48
|date=26 February 1982}}</ref>

In the discharge chamber, [[microwave]] (MW) energy flows into the center containing a high level of [[ion]]s (I), causing neutral species in the gaseous [[Rocket propellant|propellant]] to ionize. Excited species flow out (FES) through the low ion region (II) to a neutral region (III) where the ions complete their [[Plasma recombination|recombination]], replaced with the flow of neutral species (FNS) towards the center. Meanwhile, energy is lost to the chamber walls through heat [[Thermal conduction|conduction]] and [[Convection (heat transfer)|convection]] (HCC), along with [[radiation]] (Rad). The remaining energy absorbed into the gaseous propellant is converted into [[thrust]].