Editing Ion thruster (section)

== Missions ==
Ion thrusters have many in-space propulsion applications. The best applications make use of the long mission interval when significant [[thrust]] is not needed. Examples of this include orbit transfers, [[Spacecraft attitude control|attitude]] adjustments, [[drag (physics)|drag]] compensation for [[low Earth orbit]]s, fine adjustments for scientific missions and cargo transport between [[propellant depot]]s, e.g., for chemical fuels. Ion thrusters can also be used for interplanetary and deep-space missions where acceleration rates are not crucial. Ion thrusters are seen as the best solution for these missions, as they require high change in velocity but do not require rapid acceleration. Continuous thrust over long durations can reach high velocities while consuming far less propellant than traditional chemical rockets.

=== Demonstration vehicles ===
==== SERT ====
Ion propulsion systems were first demonstrated in space by the [[NASA Glenn Research Center|NASA Lewis]] (now Glenn Research Center) missions [[SERT-1|Space Electric Rocket Test (SERT)-1]] and SERT-2A.<ref name="Sovey" /> A [[SERT-1]] suborbital flight was launched on 20 July 1964, and successfully proved that the technology operated as predicted in space. These were [[electrostatic ion thruster]]s using [[Mercury (element)|mercury]] and [[caesium]] as the reaction mass. SERT-2A, launched on 4 February 1970,<ref name="sert2"/><ref>[http://www.astronautix.com/craft/sert.htm SERT page] {{webarchive|url=https://web.archive.org/web/20101025005136/http://www.astronautix.com/craft/sert.htm|date=2010-10-25}} at Astronautix (Accessed July 1, 2010).</ref> verified the operation of two mercury ion engines for thousands of running hours.<ref name="sert2"/>

=== Operational missions ===
Ion thrusters are routinely used for station-keeping on commercial and military communication satellites in geosynchronous orbit. The Soviet Union pioneered this field, using [[Hall-effect thruster|stationary plasma thrusters]] (SPTs) on satellites starting in the early 1970s.

Two geostationary satellites (ESA's [[Artemis (satellite)|Artemis]] in 2001–2003<ref>{{cite web|url=http://www.esa.int/esaTE/SEM1LT0P4HD_index_0.html|title=Artemis team receives award for space rescue |access-date=2006-11-16|publisher=ESA}}</ref> and the United States military's [[AEHF-1]] in 2010–2012<ref>{{cite web|url=http://www.airforce-magazine.com/MagazineArchive/Pages/2012/January%202012/0112space.aspx|archive-url=https://web.archive.org/web/20120109095137/http://www.airforce-magazine.com/MagazineArchive/Pages/2012/January%202012/0112space.aspx|url-status=usurped|archive-date=9 January 2012|title=Rescue in Space}}</ref>) used the ion thruster to change orbit after the chemical-propellant engine failed. [[Boeing]]<ref>{{cite web |url=http://spaceflightnow.com/news/n1203/19boeing702sp/|title=Electric propulsion could launch new commercial trend|publisher=Spaceflight Now}}</ref> began using ion thrusters for station-keeping in 1997 and planned in 2013–2014 to offer a variant on their 702 platform, with no chemical engine and ion thrusters for orbit raising; this permits a significantly lower launch mass for a given satellite capability. [[AEHF-2]] used a chemical engine to raise perigee to {{cvt|16330|km}} and proceeded to [[geosynchronous orbit]] using electric propulsion.<ref name=aehf2-sfn>{{cite web |url=https://spaceflightnow.com/atlas/av031/lae/|title=Spaceflight Now &#124; Atlas Launch Report &#124; AEHF 2 communications satellite keeps on climbing|website=spaceflightnow.com}}</ref>

==== In Earth orbit ====
===== Tiangong space station =====
China's [[Tiangong space station]] is fitted with ion thrusters. Its [[Tianhe core module]] is propelled by both chemical thrusters and four Hall-effect thrusters,<ref>{{cite web|url=https://spectrum.ieee.org/everything-you-need-to-know-about-chinas-space-station-tianhe-launch|title=Three Decades in the Making, China's Space Station Launches This Week |website=IEEE |date=28 April 2021 |first=Andrew |last=Jones}}</ref> which are used to adjust and maintain the station's orbit. The development of the Hall-effect thrusters is considered a sensitive topic in China, with scientists "working to improve the technology without attracting attention". Hall-effect thrusters are created with crewed mission safety in mind with effort to prevent erosion and damage caused by the accelerated ion particles. A magnetic field and specially designed ceramic shield was created to repel damaging particles and maintain integrity of the thrusters. According to the [[Chinese Academy of Sciences]], the ion drive used on Tiangong has burned continuously for 8,240 hours without a glitch, indicating their suitability for the Chinese space station's designated 15-year lifespan.<ref>{{cite web|url=https://www.scmp.com/news/china/science/article/3135770/how-chinas-space-station-could-help-power-astronauts-mars |title=How China's space station could help power astronauts to Mars |date=2 June 2021 |first=Stephen |last=Chen}}</ref> This is the world's first Hall thruster on a human-rated mission.<ref name="human_ion" />

===== Starlink =====
[[SpaceX]]'s [[Starlink]] [[satellite constellation]] uses [[Hall-effect thruster]]s powered by [[krypton]] or [[argon]] to raise orbit, perform maneuvers, and de-orbit at the end of their use.<ref>{{cite web |url=https://techcrunch.com/2019/05/24/spacex-reveals-more-starlink-info-after-launch-of-first-60-satellites/|title=SpaceX reveals more Starlink info after launch of first 60 satellites|date=24 May 2019 |access-date=30 July 2020}}</ref>

===== GOCE =====
[[ESA]]'s [[Gravity Field and Steady-State Ocean Circulation Explorer]] (GOCE) was launched on 16 March 2009. It used ion propulsion throughout its twenty-month mission to combat the air-drag it experienced in its low orbit (altitude of 255 kilometres) before intentionally deorbiting on 11 November 2013.

==== In deep space ====
===== Deep Space 1 =====
[[NASA]] developed the [[NASA Solar Technology Application Readiness|NSTAR]] ion engine for use in interplanetary science missions beginning in the late 1990s. It was space-tested in the space probe ''[[Deep Space 1]]'', launched in 1998. This was the first use of electric propulsion as the interplanetary propulsion system on a science mission.<ref name="Sovey"/> Based on the NASA design criteria, [[HRL Laboratories|Hughes Research Labs]] developed the [[Gridded ion thruster|Xenon Ion Propulsion System]] (XIPS) for performing [[orbital station-keeping|station keeping]] on [[geosynchronous satellite]]s.<ref>{{cite journal |author1=Rawlin |first=V. K. |author2=Patterson |first2=M. J/ |author3=Gruber |first3=R. P. |date=1990 |title=Xenon Ion Propulsion for Orbit Transfer |url=https://ntrs.nasa.gov/api/citations/19910002485/downloads/19910002485.pdf |url-status=live |journal=NASA Technical Memorandum 103193 |issue=AIAA-90-2527 |page=5 |archive-url=https://ghostarchive.org/archive/20221009/https://ntrs.nasa.gov/api/citations/19910002485/downloads/19910002485.pdf |archive-date=2022-10-09 |access-date=25 January 2022}}</ref> [[L3Harris Electron Devices|Hughes (EDD)]] manufactured the NSTAR thruster used on the spacecraft.

===== Hayabusa and Hayabusa2 =====
The [[JAXA|Japanese Aerospace Exploration Agency's]] [[Hayabusa (spacecraft)|''Hayabusa'']] space probe was launched in 2003 and rendezvoused with the asteroid [[25143 Itokawa]]. It was powered by four xenon ion engines, which used microwave [[electron cyclotron resonance]] to ionize the propellant and an erosion-resistant carbon/carbon-composite material for its acceleration grid.<ref>{{cite web|url=http://www.ep.isas.ac.jp/muses-c/|title=小惑星探査機はやぶさ搭載イオンエンジン (Ion Engines used on Asteroid Probe Hayabusa)|access-date=2006-10-13|publisher=ISAS |language=ja|url-status=dead|archive-url=https://web.archive.org/web/20060819093452/http://www.ep.isas.ac.jp/muses-c/|archive-date=2006-08-19}}</ref> Although the ion engines on ''Hayabusa'' experienced technical difficulties, in-flight reconfiguration allowed one of the four engines to be repaired and allowed the mission to successfully return to Earth.<ref>{{cite news|first=Hiroko |last=Tabuchi |author-link=Hiroko Tabuchi |url=https://www.nytimes.com/2010/07/02/business/global/02space.html |title=Faulty Space Probe Seen as Test of Japan's Expertise |newspaper=The New York Times |date=1 July 2010}}</ref>

[[Hayabusa2]], launched in 2014, was based on Hayabusa. It also used ion thrusters.<ref>Nishiyama, Kazutaka; Hosoda, Satoshi; Tsukizaki, Ryudo; Kuninaka, Hitoshi. [https://jaxa.repo.nii.ac.jp/?action=repository_uri&item_id=15670&file_id=31&file_no=1 Operation Status of Ion Engines of Asteroid Explorer Hayabusa2], [[JAXA]], January 2017.</ref>

===== Smart 1 =====
The [[European Space Agency]]'s satellite ''[[SMART-1]]'' launched in 2003 using a [[Safran Aircraft Engines|Snecma]] [[PPS-1350]]-G Hall thruster to get from [[Geostationary transfer orbit|GTO]] to lunar orbit. This satellite completed its mission on 3 September 2006, in a controlled collision on the [[Moon]]'s surface, after a trajectory deviation so scientists could see the 3-meter crater the impact created on the visible side of the Moon.

===== Dawn =====
[[Dawn (spacecraft)|''Dawn'']] launched on 27 September 2007, to explore the asteroid [[4 Vesta|Vesta]] and the dwarf planet [[Ceres (dwarf planet)|Ceres]]. It used three ''[[Deep Space 1]]'' heritage xenon ion thrusters (firing one at a time). ''Dawn''{{'s}} ion drive is capable of accelerating from 0 to {{cvt|97|km/h}} in 4 days of continuous firing.<ref>[http://www.jpl.nasa.gov/news/features.cfm?feature=1468 The Prius of Space] {{Webarchive|url=https://web.archive.org/web/20110605015515/http://www.jpl.nasa.gov/news/features.cfm?feature=1468 |date=5 June 2011 }}, 13 September 2007, NASA Jet Propulsion Laboratory {{PD-notice}}</ref> The mission ended on 1 November 2018, when the spacecraft ran out of [[hydrazine]] chemical propellant for its attitude thrusters.<ref name="DawnEOM">{{cite web|url=https://www.nasa.gov/press-release/nasa-s-dawn-mission-to-asteroid-belt-comes-to-end|title=NASA's Dawn Mission to Asteroid Belt Comes to End|date=1 November 2018 |publisher=NASA}} {{PD-notice}}</ref>

==== LISA Pathfinder ====
[[LISA Pathfinder]] is an [[ESA]] spacecraft launched in 2015 to orbit the Sun-Earth L1 point. It does not use ion thrusters as its primary propulsion system, but uses both [[colloid thruster]]s and [[FEEP]] for precise [[Spacecraft attitude control|attitude control]] – the low thrusts of these propulsion devices make it possible to move the spacecraft incremental distances accurately. It is a test for the [[Laser Interferometer Space Antenna|LISA]] mission. The mission ended on 30 December 2017.

==== BepiColombo ====
[[ESA]]'s [[BepiColombo]] mission was launched to [[Mercury (planet)|Mercury]] on 20 October 2018.<ref name="BepiLaunch">{{cite web |url=https://www.esa.int/Our_Activities/Operations/BepiColombo_s_beginning_ends|title=BepiColombo's beginning ends|date=22 October 2018|access-date=1 November 2018|publisher=ESA}}</ref> It uses ion thrusters in combination with [[gravity assist|swing-bys]] to get to Mercury, where a chemical rocket will complete orbit insertion.

==== Double Asteroid Redirection Test ====
NASA's [[Double Asteroid Redirection Test]] (DART) was launched in 2021 and operated its [[NEXT-C]] xenon ion thruster for about 1,000 hours to reach the target asteroid on 28 September 2022.

==== Psyche ====
NASA's [[Psyche (spacecraft)|Psyche spacecraft]] was launched in 2023 and is operating its [[SPT-140]] xenon ion thruster in order to reach asteroid [[16 Psyche]] in August 2029.

=== Proposed missions ===
==== International Space Station ====
{{as of|2011|March}}, a future launch of an Ad Astra VF-200 {{nowrap|200 kW}} [[VASIMR]] electromagnetic thruster was under consideration for testing on the [[International Space Station]] (ISS).<ref name="aaESummary20100124">{{cite web|url=http://www.adastrarocket.com/EXECUTIVE%20SUMMARY240110.pdf|title=Executive summary|date=January 24, 2010|publisher=Ad Astra Rocket Company|access-date=2010-02-27|url-status=dead|archive-url=https://web.archive.org/web/20100331171616/http://www.adastrarocket.com/EXECUTIVE%20SUMMARY240110.pdf|archive-date=March 31, 2010}}</ref><ref name="dn20080807">{{cite web |url=http://dsc.discovery.com/news/2008/08/07/plasma-rocket.html|title=Plasma Rocket May Be Tested at Space Station|date=7 August 2008|first=Irene|last=Klotz|publisher=Discovery News|access-date=2010-02-27}}</ref> However, in 2015, NASA ended plans for flying the VF-200 to the ISS. A NASA spokesperson stated that the ISS "was not an ideal demonstration platform for the desired performance level of the engines". Ad Astra stated that tests of a VASIMR thruster on the ISS would remain an option after a future in-space demonstration.<ref name="VASiMRscrapped">Irene Klotz (17 March 2015). [http://sen.com/blogs/irene-klotz/nasa-nixes-ad-astra-rocket-test-on-the-space-station NASA nixes Ad Astra rocket test on the space station] ''SEN News.''</ref>

The VF-200 would have been a flight version of the [[VX-200]].<ref name="Yahoo News">{{cite web|url=https://news.yahoo.com/nasa-test-vf-200-vasimr-plasma-rocket-iss-20110310-155100-110.html|title=NASA to Test VF-200 VASIMR Plasma Rocket at the ISS|date=March 10, 2011|first=Mark|last=Whittington|publisher=Yahoo|access-date=2012-01-27}}</ref><ref name="Yahoo">{{cite news |url=http://www.dailytech.com/Commercially+Developed+Plasma+Engine+Soon+To+Be+Tested+In+Space/article12612.htm|title=Commercially Developed Plasma Engine Soon to be Tested in Space|date=August 11, 2008 |first=Jason|last=Mick|publisher=DailyTech|access-date=2010-02-27|archive-url=https://web.archive.org/web/20150222124839/http://www.dailytech.com/Commercially+Developed+Plasma+Engine+Soon+To+Be+Tested+In+Space/article12612.htm|archive-date=February 22, 2015|url-status=dead}}</ref> Since the available power from the ISS is less than 200&nbsp;kW, the ISS VASIMR would have included a trickle-charged battery system allowing for 15 minutes pulses of thrust. The ISS orbits at a relatively [[low Earth orbit|low altitude]] and experiences fairly high levels of [[atmospheric drag]], requiring [[orbital station-keeping|periodic altitude boosts]] – a high-efficiency engine (high specific impulse) for station-keeping would be valuable; theoretically VASIMR reboosting could cut fuel cost from the current US$210 million annually to one-twentieth.<ref name="aaESummary20100124"/> VASIMR could in theory use as little as 300&nbsp;kg of argon gas for ISS station-keeping instead of 7500&nbsp;kg of chemical fuel – the high exhaust velocity (high [[specific impulse]]) would achieve the same acceleration with a smaller amount of propellant, compared to chemical propulsion with its lower exhaust velocity needing more fuel.<ref name="newscientist.com">{{cite web|last=Shiga|first=David|url=https://www.newscientist.com/article/dn17918-rocket-company-tests-worlds-most-powerful-ion-engine/|title=Rocket company tests world's most powerful ion engine|publisher=New Scientist|date=2009-10-05|access-date=2019-11-16}}</ref> [[Hydrogen]] is generated by the ISS as a by-product and is vented into space.

NASA previously worked on a 50&nbsp;kW Hall-effect thruster for the ISS, but work was stopped in 2005.<ref name="newscientist.com"/>

==== Lunar Gateway ====
The [[Power and Propulsion Element|Power and Propulsion Element (PPE)]] is a module on the [[Lunar Gateway]] that provides power generation and propulsion capabilities. It is targeting launch on a commercial vehicle in January 2024.<ref>{{cite web |url=https://www.oversight.gov/sites/default/files/oig-reports/IG-21-004.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.oversight.gov/sites/default/files/oig-reports/IG-21-004.pdf |archive-date=2022-10-09 |url-status=live |title=Report No. IG-21-004: NASA's Management of the Gateway Program for Artemis Missions |pages=5–7 |work=[[Office of Inspector General (United States)|OIG]] |publisher=[[NASA]] |date=10 November 2020 |access-date=28 December 2020}}</ref> It would probably use the 50&nbsp;kW [[Advanced Electric Propulsion System]] (AEPS) under development at NASA [[Glenn Research Center]] and [[Aerojet Rocketdyne]].<ref name="AEPS 2017">Daniel A. Herman, Todd A. Tofil, Walter Santiago, Hani Kamhawi, James E. Polk, John S. Snyder, Richard R. Hofer, Frank Q. Picha, Jerry Jackson and May Allen. [https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20180001297.pdf Overview of the Development and Mission Application of the Advanced Electric Propulsion System (AEPS)], NASA/TM—2018-219761 35th International Electric Propulsion Conference, Atlanta, Georgia, 8–12 October 2017, Accessed: 27 July 2018.</ref>

==== MARS-CAT ====
The MARS-CAT (Mars Array of ionospheric Research Satellites using the CubeSat Ambipolar Thruster) mission is a two 6U [[CubeSat]] concept mission to study Mars' ionosphere. The mission would investigate its plasma and magnetic structure, including transient plasma structures, magnetic field structure, magnetic activity and correlation with solar wind drivers.<ref name="MARS-CAT"/> The CAT thruster is now called the [[Radio frequency|RF]] thruster and manufactured by Phase Four.<ref name="P4_RF_Thruster"/>

==== Interstellar missions ====
[[Geoffrey A. Landis]] proposed using an ion thruster powered by a space-based laser, in conjunction with a lightsail, to propel an interstellar probe.<ref>{{cite journal |last=Landis |first=Geoffrey A. |date=1991 |title=Laser-Powered Interstellar Probe |journal=[[APS Bulletin]] |volume=36 |issue=5 |pages=1687–1688}}</ref><ref>{{cite web|url=http://www.geoffreylandis.com/laser_ion.htp |first=Geoffrey A. |last=Landis |title=Laser-powered Interstellar Probe |date=1994 |archive-url=https://web.archive.org/web/20120722013713/http://www.geoffreylandis.com/laser_ion.htp |archive-date=2012-07-22 |work=GeoffreyLandis.com}}</ref>