Editing Hall-effect thruster (section)

====External discharge Hall thruster====
Sputtering erosion of discharge channel walls and pole pieces that protect the magnetic circuit causes failure of thruster operation. Therefore, annular and cylindrical Hall thrusters have limited lifetime. Although magnetic shielding has been shown to dramatically reduce discharge channel wall erosion, pole piece erosion is still a concern.<ref>{{Cite book |chapter=Pole-piece Interactions with the Plasma in a Magnetically Shielded Hall Thruster |title=50th AIAA/ASME/SAE/ASEE Joint Propulsion Conference |doi=10.2514/6.2014-3899 |isbn=978-1-62410-303-2 |date=2014 |last1=Goebel |first1=Dan M. |last2=Jorns |first2=Benjamin |last3=Hofer |first3=Richard R. |last4=Mikellides |first4=Ioannis G. |last5=Katz |first5=Ira }}</ref> As an alternative, an unconventional Hall&nbsp;thruster design called external discharge Hall thruster or external discharge plasma thruster (XPT) has been introduced.<ref>{{Cite book |chapter=Preliminary Investigation of an External Discharge Plasma Thruster |title=52nd AIAA/SAE/ASEE Joint Propulsion Conference |doi=10.2514/6.2016-4951 |isbn=978-1-62410-406-0 |date=2016 |last1=Karadag |first1=Burak |last2=Cho |first2=Shinatora |last3=Oshio |first3=Yuya |last4=Hamada |first4=Yushi |last5=Funaki |first5=Ikkoh |last6=Komurasaki |first6=Kimiya }}</ref><ref>{{Cite web|url=https://repository.exst.jaxa.jp/dspace/bitstream/a-is/549895/1/SA6000036090.pdf|title=Numerical Investigation of an External Discharge Hall Thruster Design Utilizing Plasma-lens Magnetic Field|url-status=live|archive-url=https://web.archive.org/web/20170814095202/https://repository.exst.jaxa.jp/dspace/bitstream/a-is/549895/1/SA6000036090.pdf|archive-date=14 August 2017}}</ref><ref>{{Cite web|url=http://ltu.diva-portal.org/smash/record.jsf?pid=diva2%3A1037721&dswid=1358|title=Low–voltage External Discharge Plasma Thruster and Hollow Cathodes Plasma Plume Diagnostics Utilising Electrostatic Probes and Retarding Potential Analyser|url-status=live|archive-url=https://web.archive.org/web/20170829163334/http://ltu.diva-portal.org/smash/record.jsf?pid=diva2%3A1037721&dswid=1358|archive-date=29 August 2017}}</ref> The external discharge Hall thruster does not possess any discharge channel walls or pole pieces. Plasma discharge is produced and sustained completely in the open space outside the thruster structure, and thus erosion-free operation is achieved.