Editing Ion thruster (section)

== Lifetime ==
Ion thrusters' low thrust requires continuous operation for a long time to achieve the necessary change in velocity ([[delta-v]]) for a particular mission. Ion thrusters are designed to provide continuous operation for intervals of weeks to years.

The lifetime of electrostatic ion thrusters is limited by several processes.

=== Gridded thruster life===
In electrostatic gridded designs, charge-exchange ions produced by the beam ions with the neutral gas flow can be accelerated towards the negatively biased accelerator grid and cause grid erosion. End-of-life is reached when either the grid structure fails or the holes in the grid become large enough that ion extraction is substantially affected – e.g., by the occurrence of electron backstreaming. Grid erosion cannot be avoided and is the major lifetime-limiting factor. Thorough grid design and material selection enable lifetimes of 20,000 hours or more.

A test of the [[NASA Solar Technology Application Readiness]] (NSTAR) electrostatic ion thruster resulted in 30,472 hours (roughly 3.5 years) of continuous thrust at maximum power. Post-test examination indicated the engine was not approaching failure.<ref>{{cite web|url=http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/39521/1/05-2793.pdf|title=Destructive Physical Analysis of Hollow Cathodes from the Deep Space 1 Flight Spare Ion Engine 30,000 Hour Life Test|access-date=2007-11-21|url-status=dead|archive-url=https://web.archive.org/web/20090227050954/http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/39521/1/05-2793.pdf|archive-date=2009-02-27}} {{PD-notice}}</ref><ref name=autogenerated1/><ref name="Choueiri"/> NSTAR operated for years on ''Dawn''.

The [[NASA Evolutionary Xenon Thruster]] (NEXT) project operated continuously for more than 48,000 hours.<ref>{{cite web |title=NASA Thruster Achieves World – Record 5+ Years of Operation |url=http://spacefellowship.com/news/art34276/nasa-thruster-achieves-world-record-5-years-of-operation.html |access-date=2012-06-27}}</ref> The test was conducted in a high-vacuum test chamber. Over the course of the test, which lasted more than five and a half years, the engine consumed approximately 870 kilograms of xenon propellant. The total impulse generated would require over 10,000 kilograms of conventional rocket propellant for a similar application.

===Hall-effect thruster life===
Hall-effect thrusters suffer from strong erosion of the ceramic discharge chamber by impact of energetic ions: a test reported in 2010 <ref name="leipzig">{{cite web|url=http://www.uni-leipzig.de/~iom/muehlleithen/2010/Bundesmann_2010.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.uni-leipzig.de/~iom/muehlleithen/2010/Bundesmann_2010.pdf |archive-date=2022-10-09 |url-status=live|title=A closer look at a stationary plasma thruster}}</ref> showed erosion of around 1&nbsp;mm per hundred hours of operation, though this is inconsistent with observed on-orbit lifetimes of a few thousand hours.

The [[Advanced Electric Propulsion System]] (AEPS) is expected to accumulate about 5,000 hours and the design aims to achieve a flight model that offers a half-life of at least 23,000 hours<ref name='AEPS 2017'/> and a full life of about 50,000 hours.<ref name="Rocketdyne 2016">[http://rocket.com/article/aerojet-rocketdyne-signs-contract-develop-advanced-electric-propulsion-system-nasa Aerojet Rocketdyne Signs Contract to Develop Advanced Electric Propulsion System for NASA] Aerojet Rocketdyne Press release, 28 April 2016 Accessed: 27 July 2018.</ref>