Editing Spacecraft propulsion (section)

===Electric propulsion===
[[File:Ion Engine Test Firing - GPN-2000-000482.jpg|thumb|right|upright=1.2|NASA's 2.3 kW NSTAR [[ion thruster]] for the [[Deep Space&nbsp;1]] spacecraft during a hot fire test at the Jet Propulsion Laboratory]]{{Main|Spacecraft electric propulsion}}

[[File:Xenon hall thruster.jpg|thumb|6 kW Hall thruster in operation at the [[NASA]] [[Jet Propulsion Laboratory]] ]]

Rather than relying on high temperature and [[fluid dynamics]] to accelerate the reaction mass to high speeds, there are a variety of methods that use electrostatic or [[electromagnetism|electromagnetic]] forces to accelerate the reaction mass directly, where the reaction mass is usually a stream of [[ion]]s.{{citation needed|date = July 2023}}

Ion propulsion rockets typically heat a plasma or charged gas inside a [[magnetic bottle]] and release it via a [[magnetic nozzle]] so that no solid matter needs to come in contact with the plasma.<ref>{{Cite web |title=NASA Facts - Ion Propulsion |url=https://www.nasa.gov/wp-content/uploads/2015/08/ionpropfact_sheet_ps-01628.pdf |access-date=May 18, 2024 |website=[[NASA]]}}</ref> Such an engine uses electric power, first to ionize atoms, and then to create a voltage gradient to accelerate the ions to high exhaust velocities.<ref>{{Cite web |title=Ion Propulsion – NASA Science |url=https://science.nasa.gov/mission/dawn/technology/ion-propulsion/ |access-date=2024-04-25 |website=science.nasa.gov |date=23 October 2018 |language=en-US}}</ref> For these drives, at the highest exhaust speeds, energetic efficiency and thrust are all inversely proportional to exhaust velocity.{{citation needed|date = July 2023}} Their very high exhaust velocity means they require huge amounts of energy and thus with practical power sources provide low thrust, but use hardly any fuel.{{citation needed|date = July 2023}}

[[electrically powered spacecraft propulsion|Electric propulsion]] is commonly used for station keeping on commercial [[communications satellites]] and for prime propulsion on some [[space exploration|scientific space missions]] because of their high specific impulse.<ref>{{Cite web |title=Space Power Chapter 7: Electric Rockets – Opening the Solar System – NSS |date=3 August 2017 |url=https://nss.org/space-power-chapter-7-electric-rockets-opening-the-solar-system/ |access-date=2024-04-28 |language=en-US}}</ref> However, they generally have very small values of thrust and therefore must be operated for long durations to provide the total impulse required by a mission.{{Sfn|Meyer|2012|p=5}}<ref name="tomsik">Tomsik, Thomas M. "[http://thehuwaldtfamily.org/jtrl/research/Propulsion/Rocket%20Propulsion/NASA-TM-2000-209941,%20Advances%20in%20Cryo%20Propellant%20Densification%20Technology.pdf Recent advances and applications in cryogenic propellant densification technology] {{Webarchive|url=https://web.archive.org/web/20141129035753/http://thehuwaldtfamily.org/jtrl/research/Propulsion/Rocket%20Propulsion/NASA-TM-2000-209941,%20Advances%20in%20Cryo%20Propellant%20Densification%20Technology.pdf|date=2014-11-29}}." NASA TM 209941 (2000).</ref><ref name="oleson">Oleson, S., and Sankovic, J. "[http://adsabs.harvard.edu/full/2000ESASP.465..717O Advanced Hall electric propulsion for future in-space transportation]." Spacecraft Propulsion. Vol. 465. 2000.</ref><ref>Dunning, John W., Scott Benson, and Steven Oleson. "NASA's electric propulsion program." 27th International Electric Propulsion Conference, Pasadena, California, IEPC-01-002. 2001.</ref>

The idea of electric propulsion dates to 1906, when [[Robert Goddard (scientist)|Robert Goddard]] considered the possibility in his personal notebook.<ref name="choueiri">{{cite journal | last = Choueiri | first = Edgar Y. | year = 2004 | title = A Critical History of Electric Propulsion: The First 50 Years (1906–1956) | journal = Journal of Propulsion and Power | volume = 20 | issue = 2 | pages = 193–203 | url = http://alfven.princeton.edu/publications/choueiri-jpp-2004 | doi = 10.2514/1.9245 | citeseerx = 10.1.1.573.8519 | access-date = 2016-10-18 | archive-date = 2019-04-28 | archive-url = https://web.archive.org/web/20190428155604/https://alfven.princeton.edu/publications/choueiri-jpp-2004 }}</ref> [[Konstantin Tsiolkovsky]] published the idea in 1911.<ref>{{Cite journal |last=Choueiri |first=Edgar |date=2004-06-26 |title=A Critical History of Electric Propulsion: The First Fifty Years (1906-1956) |url=http://dx.doi.org/10.2514/6.2004-3334 |journal=40th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit |location=Reston, Virginia |publisher=American Institute of Aeronautics and Astronautics |doi=10.2514/6.2004-3334|isbn=978-1-62410-037-6 }}</ref>

Electric propulsion methods include:<ref>{{Cite web |title=4.0 In-Space Propulsion – NASA |url=https://www.nasa.gov/smallsat-institute/sst-soa/in-space_propulsion/ |access-date=2024-04-28 |language=en-US}}</ref>
* [[Ion thrusters]], which accelerate ions first and later neutralize the ion beam with an electron stream emitted from a cathode called a neutralizer;<ref>{{Cite web |title=Deep Space 1: Advanced Technologies: Solar Electric Propulsion FAQ |url=https://www.jpl.nasa.gov/nmp/ds1/tech/ionpropfaq.html |access-date=2024-04-28 |website=www.jpl.nasa.gov}}</ref>
**[[Electrostatic ion thruster]]s
**[[Field-emission electric propulsion]]
**[[MagBeam]] thrusters
**[[Hall-effect thruster]]s
**[[Colloid thruster]]s
* Electrothermal thrusters, wherein electromagnetic fields are used to generate a plasma to increase the [[heat]] of the bulk propellant, the thermal energy imparted to the propellant gas is then converted into kinetic energy by a [[nozzle]] of either physical material construction or by magnetic means;{{citation needed|date = July 2023}}
**[[Arcjet]]s using DC current or microwaves
**[[Helicon double-layer thruster]]s
**[[Resistojet]]s
* Electromagnetic thrusters, wherein ions are accelerated either by the [[Lorentz Force]] or by the effect of electromagnetic fields where the electric field is not in the direction of the acceleration;{{citation needed|date = July 2023}}
**[[Plasma propulsion engine]]s
**[[Magnetoplasmadynamic thruster]]s
**[[Electrodeless plasma thruster]]s
**[[Pulsed inductive thruster]]s
**[[Pulsed plasma thruster]]s
**[[Variable specific impulse magnetoplasma rocket]]s (VASIMR)
**[[Vacuum arc thruster]]s
*[[Mass driver]]s designed for propulsion.{{citation needed|date = July 2023}}

====Power sources====
For some missions, particularly reasonably close to the Sun, [[solar energy]] may be sufficient, and has often been used, but for others further out or at higher power, nuclear energy is necessary; engines drawing their power from a nuclear source are called [[nuclear electric rocket]]s.<ref>{{Cite web |title=Space Nuclear Propulsion – NASA |url=https://www.nasa.gov/tdm/space-nuclear-propulsion/ |access-date=2024-04-28 |language=en-US}}</ref>

Current nuclear power generators are approximately half the weight of solar panels per watt of energy supplied, at terrestrial distances from the Sun.{{citation needed|date = July 2023}} Chemical power generators are not used due to the far lower total available energy.<ref>{{Cite web |last=Luckenbaugh |first=Josh |date=July 31, 2023 |title=Government, Industry Explore Nuclear, Solar Space Engines |url=https://www.nationaldefensemagazine.org/articles/2023/7/31/government-industry-explore-nuclear-solar-space-engines |access-date=2024-04-28 |website=www.nationaldefensemagazine.org}}</ref> Beamed power to the spacecraft is considered to have potential, according to NASA and the [[University of Colorado Boulder]].<ref>{{Cite web |date=2021 |title=Beamed Laser Power for UAVs |url=https://www.nasa.gov/wp-content/uploads/2021/09/120329main_fs-087-dfrc.pdf |access-date=April 24, 2024 |website=[[NASA]]}}</ref><ref>{{Cite web |last=Beam Propulsion |first=Chuck |date=November 28, 2007 |title=Beam Propulsion |url=https://www.colorado.edu/faculty/kantha/sites/default/files/attached-files/final_vaughan.pdf#:~:text=If%20efficient%20magnetic%20nozzles%20can,as%20well%20as%20interplanetary%20missions. |access-date=April 24, 2024 |website=[[University of Colorado Boulder]]}}</ref>

With any current source of electrical power, chemical, nuclear or solar, the maximum amount of power that can be generated limits the amount of thrust that can be produced to a small value.{{citation needed|date = July 2023}} Power generation adds significant mass to the spacecraft, and ultimately the weight of the power source limits the performance of the vehicle.<ref>{{Cite web |title=3.0 Power – NASA |url=https://www.nasa.gov/smallsat-institute/sst-soa/power-subsystems/ |access-date=2024-04-28 |language=en-US}}</ref>