Editing Spacecraft propulsion (section)

==Propulsion technology==
Spacecraft propulsion technology can be of several types, such as chemical, electric or nuclear. They are distinguished based on the physics of the propulsion system and how thrust is generated. Other experimental and more theoretical types are also included, depending on their technical maturity. Additionally, there may be credible meritorious in-space propulsion concepts not foreseen or reviewed at the time of publication, and which may be shown to be beneficial to future mission applications.{{Sfn|Meyer|2012|p=10}}

Almost all types are [[reaction engine]]s, which produce [[thrust]] by expelling [[reaction mass]], in accordance with [[Newton's third law of motion]].<ref>{{Cite web |title=AMT Handbook |url=https://www.faa.gov/sites/faa.gov/files/03_amtp_ch1.pdf |access-date=April 20, 2024 |website=www.faa.gov}}</ref><ref>{{Cite web |title=Rocket Principles |url=https://www.grc.nasa.gov/www/k-12/rocket/TRCRocket/rocket_principles.html |access-date=April 20, 2024 |website=[[NASA]]}}</ref><ref><!--THIS IS UNNECESSARY, IN THIS DITOR'S VIEW:-->This law of motion is most commonly paraphrased as: "For every action force there is an equal, but opposite, reaction force."{{citation needed|date = July 2023}}</ref> Examples include [[jet engine]]s, [[rocket engine]]s, [[pump-jet]], and more uncommon variations such as [[Hall-effect thruster|Hall–effect thrusters]], [[ion drive]]s, [[mass drivers]], and [[nuclear pulse propulsion]].<ref>{{Cite web |title=Chapter 11: Onboard Systems – NASA Science |url=https://science.nasa.gov/learn/basics-of-space-flight/chapter11-4/ |access-date=2024-04-19 |website=science.nasa.gov |date=20 July 2023 |language=en-US}}</ref>

===Chemical propulsion===
{{Main|Rocket engine}}

[[File:SpaceX engine test fire.jpg|thumb|right|[[SpaceX]]'s [[Kestrel (rocket engine)|Kestrel engine]] is tested.]]

A large fraction of [[rocket engine]]s in use today are [[Rocket engine#Chemically powered|chemical rockets]]; that is, they obtain the energy needed to generate thrust by [[chemical reactions]] to create a hot gas that is expanded to produce [[thrust]].<ref>{{Cite web |title=Chapter 14: Launch – NASA Science |url=https://science.nasa.gov/learn/basics-of-space-flight/chapter14-1/ |access-date=2024-04-19 |website=science.nasa.gov |date=20 July 2023 |language=en-US}}</ref> Many different propellant combinations are used to obtain these chemical reactions, including, for example, [[hydrazine]], [[liquid oxygen]], [[liquid hydrogen]], [[nitrous oxide]], and [[hydrogen peroxide]].<ref>{{Cite web |title=4.0 In-Space Propulsion – NASA |url=https://www.nasa.gov/smallsat-institute/sst-soa/in-space_propulsion/ |access-date=2024-04-25 |language=en-US}}</ref> They can be used as a [[Monopropellant rocket|monopropellant]] or in [[Bipropellant rocket|bi-propellant]] configurations.<ref>{{Cite web |title=4.0 In-Space Propulsion – NASA |url=https://www.nasa.gov/smallsat-institute/sst-soa/in-space_propulsion/ |access-date=2024-04-20 |language=en-US}}</ref>

Rocket engines provide essentially the highest specific powers and high specific thrusts of any engine used for spacecraft propulsion.<ref name=":4" /> Most rocket engines are [[internal combustion engine|internal combustion]] [[heat engines]] (although non-combusting forms exist).<ref name="Leishman">{{Cite book |last=Leishman |first=J. Gordon |date=2023-01-01 |title=Introduction to Aerospace Flight Vehicles - Rocket Engines |url=https://eaglepubs.erau.edu/introductiontoaerospaceflightvehicles/chapter/rocket-engines/ |language=en|publisher=Embry Riddle Aeronautical University}}</ref> Rocket engines generally produce a high-temperature reaction mass, as a hot gas, which is achieved by combusting a solid, liquid or gaseous fuel with an oxidiser within a combustion chamber.<ref>{{Cite web |title=Rocket Propulsion |url=https://www.grc.nasa.gov/www/k-12/airplane/rocket.html |access-date=April 21, 2024 |website=[[NASA]]}}</ref> The extremely hot gas is then allowed to escape through a high-expansion ratio bell-shaped [[de Laval nozzle|nozzle]], a feature that gives a rocket engine its characteristic shape.<ref name="Leishman"/> The effect of the nozzle is to accelerate the mass, converting most of the thermal energy into kinetic energy,<ref name="Leishman"/> where exhaust speeds reaching as high as 10 times the speed of sound at sea level are common.{{citation needed|date = July 2023}}

====Green chemical propulsion====
The dominant form of chemical propulsion for [[satellite]]s has historically been [[hydrazine]], however, this fuel is highly toxic and at risk of being banned across Europe.<ref>{{Cite web |date=2017-10-25 |title=Hydrazine ban could cost Europe's space industry billions |url=https://spacenews.com/hydrazine-ban-could-cost-europes-space-industry-billions/ |access-date=2022-08-19 |website=SpaceNews |language=en-US}}</ref> Non-toxic 'green' alternatives are now being developed to replace hydrazine. [[Nitrous oxide]]-based alternatives are garnering traction and government support,<ref>{{Cite web |last=Urban |first=Viktoria |date=2022-07-15 |title=Dawn Aerospace granted €1.4 million by EU for green propulsion technology |url=https://spacewatch.global/2022/07/dawn-aerospace-granted-e1-4-million-by-eu-for-green-propulsion-technology/ |access-date=2022-08-19 |website=SpaceWatch.Global |language=en-US}}</ref><ref>{{Cite web |title=International research projects {{!}} Ministry of Business, Innovation & Employment |url=https://www.mbie.govt.nz/science-and-technology/space/nzspacetalk/international-research-projects/ |access-date=2022-08-19 |website=www.mbie.govt.nz}}</ref> with development being led by commercial companies Dawn Aerospace, Impulse Space,<ref>{{Cite web |last=Berger |first=Eric |date=2022-07-19 |title=Two companies join SpaceX in the race to Mars, with a launch possible in 2024 |url=https://arstechnica.com/science/2022/07/relativity-and-impulse-space-say-theyre-flying-to-mars-in-late-2024/ |access-date=2022-08-19 |website=Ars Technica |language=en-us}}</ref> and Launcher.<ref>{{Cite web |date=2021-06-15 |title=Launcher to develop orbital transfer vehicle |url=https://spacenews.com/launcher-to-develop-orbital-transfer-vehicle/ |access-date=2022-08-19 |website=SpaceNews |language=en-US}}</ref> The first nitrous oxide-based system flown in space was by D-Orbit onboard their ION Satellite Carrier ([[space tug]]) in 2021, using six [[Dawn Aerospace]] B20 thrusters, launched upon a [[SpaceX]] [[Falcon 9]] rocket.<ref>{{Cite web |title=Dawn Aerospace validates B20 Thrusters in space – Bits&Chips |date=6 May 2021 |url=https://bits-chips.nl/artikel/dawn-aerospace-validates-b20-thrusters-in-space/ |access-date=2022-08-19 |language=en-US}}</ref><ref>{{Cite web |title=Dawn B20 Thrusters Proven In Space |url=https://www.dawnaerospace.com/latest-news/b20-thrusters-proven-in-space |access-date=2022-08-19 |website=Dawn Aerospace |language=en-US}}</ref>

===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>

===Nuclear propulsion===
{{Main|Nuclear propulsion#Spacecraft}}
[[File:Plasma propulsion engine.webp|thumb|3D sketch of an [[electromagnetic propulsion]] [[Plasma propulsion engine|fusion plasma]] thruster]]
[[Nuclear fuels]] typically have very high [[specific energy]], much higher than chemical fuels, which means that they can generate large amounts of energy per unit mass. This makes them valuable in spaceflight, as it can enable high [[specific impulse]]s, sometimes even at high thrusts. The machinery to do this is complex, but research has developed methods for their use in propulsion systems, and some have been tested in a laboratory.<ref>{{Cite web |date=2018-05-25 |title=Nuclear Thermal Propulsion: Game Changing Technology for Deep Space Exploration – NASA |url=https://www.nasa.gov/directorates/stmd/tech-demo-missions-program/nuclear-thermal-propulsion-game-changing-technology-for-deep-space-exploration/ |access-date=2024-04-25 |language=en-US}}</ref>

Here, nuclear propulsion moreso refers to the source of propulsion being nuclear, instead of a [[nuclear electric rocket]] where a [[nuclear reactor]] would provide power (instead of solar panels) for other types of electrical propulsion.

Nuclear propulsion methods include:
*[[Fission-fragment rocket]]s
*[[Fission sail]]s
*[[Fusion rocket]]s
*[[Nuclear thermal rocket]]s (NTR)
*[[Nuclear pulse propulsion]]
*[[Nuclear salt-water rocket]]s
*[[Radioisotope rocket]]s

=== Without internal reaction mass ===
There are several different space drives that need little or no reaction mass to function.

==== Reaction wheels ====
Many spacecraft use [[reaction wheels]] or [[Control Moment Gyroscope|control moment gyroscopes]] to control orientation in space.<ref>{{cite journal |last=Tsiotras |first=P. |author2=Shen, H. |author3=Hall, C. D. |year=2001 |title=Satellite attitude control and power tracking with energy/momentum wheels |url=http://www.ae.gatech.edu/people/tsiotras/Papers/jgcd99.pdf |journal=Journal of Guidance, Control, and Dynamics |volume=43 |issue=1 |pages=23–34 |bibcode=2001JGCD...24...23T |citeseerx=10.1.1.486.3386 |doi=10.2514/2.4705 |issn=0731-5090}}
</ref> A satellite or other space vehicle is subject to the [[law of conservation of angular momentum]], which constrains a body from a [[net force|net change]] in [[angular velocity]]. Thus, for a vehicle to change its [[relative orientation]] without expending reaction mass, another part of the vehicle may rotate in the opposite direction. Non-conservative external forces, primarily gravitational and atmospheric, can contribute up to several degrees per day to angular momentum,<ref>{{cite book |last=King-Hele |first=Desmond |url=https://books.google.com/books?id=HSffDG356TkC&pg=PA6 |title=Satellite orbits in an atmosphere: Theory and application |publisher=Springer |year=1987 |isbn=978-0-216-92252-5 |page=6}}</ref> so such systems are designed to "bleed off" undesired rotational energies built up over time. 

====EM wave-based propulsion====
{{original research | section | date=January 2017}}
The [[Conservation law (physics)|law of conservation]] of [[momentum]] is usually taken to imply that any engine which uses no reaction mass cannot accelerate the center of mass of a spaceship (changing orientation, on the other hand, is possible).{{citation needed|date = July 2023}} But space is not empty, especially space inside the Solar System; there are gravitation fields, [[magnetic field]]s, [[electromagnetic waves]], [[solar wind]] and solar radiation.<ref>{{Cite web |title=What keeps space empty? |url=https://wtamu.edu/~cbaird/sq/2012/12/20/what-keeps-space-empty/ |access-date=2024-04-28 |website=Science Questions with Surprising Answers |language=en-US}}</ref> Electromagnetic waves in particular are known to contain momentum, despite being massless; specifically the momentum flux density '''P''' of an EM wave is quantitatively 1/c<sup>2</sup> times the [[Poynting vector]] '''S''', i.e. '''P''' = '''S'''/c<sup>2</sup>, where c is the velocity of light.{{citation needed|date = July 2023}} [[Field propulsion]] methods which do not rely on reaction mass thus must try to take advantage of this fact by coupling to a momentum-bearing field such as an EM wave that exists in the vicinity of the craft; however, because many of these phenomena are diffuse in nature, corresponding propulsion structures must be proportionately large.{{citation needed|date = July 2023}}

====Solar and magnetic sails====
[[File:Solarsail msfc.jpg|right|thumb|NASA study of a solar sail. The sail would be half a kilometer wide.]]
The concept of [[solar sail]]s rely on [[radiation pressure]] from electromagnetic energy, but they require a large collection surface to function effectively.<ref>{{Cite web |title=NASA-Supported Solar Sail Could Take Science to New Heights – NASA |url=https://www.nasa.gov/news-release/nasa-supported-solar-sail-could-take-science-to-new-heights/ |access-date=2024-04-28 |language=en-US}}</ref> [[E-sail]]s propose to use very thin and lightweight wires holding an electric charge to deflect particles, which may have more controllable directionality.{{citation needed|date = July 2023}}

[[Magnetic sail]]s deflect charged particles from the [[solar wind]] with a magnetic field, thereby imparting momentum to the spacecraft.<ref>{{Cite journal |last=Djojodihardjo |first=Harijono |date=November 2018 |title=Review of Solar Magnetic Sailing Configurations for Space Travel |url=http://link.springer.com/10.1007/s42423-018-0022-4 |journal=Advances in Astronautics Science and Technology |language=en |volume=1 |issue=2 |pages=207–219 |doi=10.1007/s42423-018-0022-4 |bibcode=2018AAnST...1..207D |issn=2524-5252}}</ref> For instance, the so-called [[Magnetic sail#Magsail (MS)|Magsail]] is a large superconducting loop proposed for acceleration/deceleration in the [[solar wind]] and deceleration in the [[Interstellar medium]].<ref>{{Cite journal |last1=Zubrin |first1=Robert M. |last2=Andrews |first2=Dana G. |date=March 1991 |title=Magnetic sails and interplanetary travel |url=https://arc.aiaa.org/doi/10.2514/3.26230 |journal=Journal of Spacecraft and Rockets |language=en |volume=28 |issue=2 |pages=197–203 |doi=10.2514/3.26230 |bibcode=1991JSpRo..28..197Z |issn=0022-4650}}</ref> A variant is the [[mini-magnetospheric plasma propulsion]] system<ref>{{Cite journal |last1=Winglee |first1=R. M. |last2=Slough |first2=J. |last3=Ziemba |first3=T. |last4=Goodson |first4=A. |date=September 2000 |title=Mini-Magnetospheric Plasma Propulsion: Tapping the energy of the solar wind for spacecraft propulsion |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/1999JA000334 |journal=Journal of Geophysical Research: Space Physics |language=en |volume=105 |issue=A9 |pages=21067–21077 |doi=10.1029/1999JA000334 |bibcode=2000JGR...10521067W |issn=0148-0227}}</ref> and its successor, the [[Magnetic sail#Magnetoplasma sail (MPS)|magnetoplasma sail]],<ref>{{Cite journal |last1=Funaki |first1=Ikkoh |last2=Asahi |first2=Ryusuke |last3=Fujita |first3=Kazuhisa |last4=Yamakawa |first4=Hiroshi |last5=Ogawa |first5=Hiroyuki |last6=Otsu |first6=Hirotaka |last7=Nonaka |first7=Satoshi |last8=Sawai |first8=Shujiro |last9=Kuninaka |first9=Hitoshi |date=2003-06-23 |title=Thrust Production Mechanism of a Magnetoplasma Sail |url=https://arc.aiaa.org/doi/10.2514/6.2003-4292 |journal=34th AIAA Plasmadynamics and Laser Conference |language=en |publisher=American Institute of Aeronautics and Astronautics |doi=10.2514/6.2003-4292 |isbn=978-1-62410-096-3}}</ref> which inject plasma at a low rate to enhance the magnetic field to more effectively deflect charged particles in a plasma wind.

Japan launched a solar sail-powered spacecraft, [[IKAROS]] in May 2010, which successfully demonstrated propulsion and guidance (and is still active as of this date).{{when|date = July 2023}}{{citation needed|date = July 2023}} As further proof of the [[solar sail]] concept, [[NanoSail-D]] became the first such powered satellite to orbit [[Earth]].<ref>{{Cite web |url= http://www.nasa.gov/mission_pages/tdm/solarsail|title=Solar Sail Demonstrator|work=NASA |date=19 September 2016 |last1=Harbaugh |first1=Jennifer }}</ref> As of August 2017, NASA confirmed the Sunjammer solar sail project was concluded in 2014 with lessons learned for future space sail projects.<ref>{{Cite web|url=https://www.nasa.gov/mission_pages/tdm/solarsail/index.html|title=Solar Sail Demonstrator|date=19 September 2016}}</ref> The U.K. [[CubeSail|Cubesail]] programme will be the first mission to demonstrate solar sailing in low Earth orbit, and the first mission to demonstrate full three-axis attitude control of a solar sail.<ref>{{cite web|title=Space Vehicle Control|url=http://www.surrey.ac.uk/ssc/research/space_vehicle_control/cubesail/news/index.htm|website=University of Surrey|access-date=8 August 2015|archive-date=7 May 2016|archive-url=https://web.archive.org/web/20160507025010/http://www.surrey.ac.uk/ssc/research/space_vehicle_control/cubesail/news/index.htm}}</ref>

====Other propulsion types====

The concept of a [[gravitational slingshot]] is a form of propulsion to carry a [[space probe]] onward to other destinations without the expense of reaction mass; harnessing the gravitational energy of other celestial objects allows the spacecraft to gain kinetic energy.<ref>{{Cite journal | year = 2004 | pages = 619–000 | doi = 10.1119/1.1621032| last2 =   Cacioppo| last3 =   Gangopadhyaya| first1 = J. J. | volume = 72| last1 = Dykla | first2 = R.| first3 = A. | journal = American Journal of Physics | title = Gravitational slingshot| issue = 5|bibcode = 2004AmJPh..72..619D | url = http://ecommons.luc.edu/cgi/viewcontent.cgi?article=1007&context=physics_facpubs}}</ref> However, more energy can be obtained from the gravity assist if rockets are used via the [[Oberth effect]].

A [[tether propulsion]] system employs a long cable with a high tensile strength to change a spacecraft's orbit, such as by interaction with a planet's magnetic field or through momentum exchange with another object.<ref>{{cite news|first=Dave |last=Drachlis |title=NASA calls on industry, academia for in-space propulsion innovations |publisher=NASA |date=October 24, 2002 |url=http://www.msfc.nasa.gov/news/news/releases/2002/02-269.html |access-date=2007-07-26 |archive-url=https://web.archive.org/web/20071206095134/http://www.msfc.nasa.gov/news/news/releases/2002/02-269.html |archive-date=December 6, 2007 }}</ref>

[[Beam-powered propulsion]] is another method of propulsion without reaction mass, and includes sails pushed by [[Laser propulsion|laser]], microwave, or particle beams.<ref>{{Cite web |date=2023-01-09 |title=Pellet-Beam Propulsion for Breakthrough Space Exploration – NASA |url=https://www.nasa.gov/general/pellet-beam-propulsion-for-breakthrough-space-exploration/ |access-date=2024-04-24 |language=en-US}}</ref>

===Advanced propulsion technology===
Advanced, and in some cases theoretical, propulsion technologies may use chemical or nonchemical physics to produce thrust but are generally considered to be of lower technical maturity with challenges that have not been overcome.{{Sfn|Meyer|2012|p=20}} For both human and robotic exploration, traversing the solar system is a struggle against time and distance. The most distant planets are 4.5–6 billion kilometers from the Sun and to reach them in any reasonable time requires much more capable propulsion systems than conventional chemical rockets. Rapid inner solar system missions with flexible launch dates are difficult, requiring propulsion systems that are beyond today's current state of the art. The logistics, and therefore the total system mass required to support sustained human exploration beyond Earth to destinations such as the Moon, Mars, or [[near-Earth object]]s, are daunting unless more efficient in-space propulsion technologies are developed and fielded.{{Sfn|Meyer|2012|p=6}}<ref name=huntsb>
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|isbn=978-0-7844-0476-8
|pages=340–346}}</ref>

A variety of hypothetical propulsion techniques have been considered that require a deeper understanding of the properties of space, particularly [[Inertial frame of reference|inertial frames]] and the [[vacuum state]]. Such methods are highly speculative and include:{{citation needed|date = July 2023}}{{colbegin}}
*[[Black hole starship]]
*[[Breakthrough Propulsion Physics Program#Quantum vacuum energy experiments|Differential sail]]
*[[Gravitational shielding]]
*[[Field propulsion]]
**Diametric drive
**Disjunction drive
**Pitch drive
**Bias drive
*[[Photon rocket]]
*[[Quantum vacuum thruster]]
*[[Nano electrokinetic thruster]]
*[[Reactionless drive]]
**[[Abraham–Minkowski controversy|Abraham—Minkowski drive]]
**[[Alcubierre drive]]
**[[Dean drive]]
**[[EmDrive]]
**[[Heim theory]]
**[[Woodward effect]]

{{colend}}

A NASA assessment of its [[Breakthrough Propulsion Physics Program]] divides such proposals into those that are non-viable for propulsion purposes, those that are of uncertain potential, and those that are not impossible according to current theories.<ref>{{cite conference
 | first =Marc
 | last =Millis
 | title =Assessing Potential Propulsion Breakthroughs
 | book-title =New Trends in Astrodynamics and Applications II
 | date =June 3–5, 2005
 | location =Princeton, NJ
 | url =https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20060000022.pdf
 }}</ref>

===Table of methods===
{{more citations needed section|date = July 2023}}
Below is a summary of some of the more popular, proven technologies, followed by increasingly speculative methods. Four numbers are shown. The first is the [[specific impulse|effective exhaust velocity]]: the equivalent speed which the propellant leaves the vehicle. This is not necessarily the most important characteristic of the propulsion method; thrust and power consumption and other factors can be. However,
* if the delta-v is much more than the exhaust velocity, then exorbitant amounts of fuel are necessary (see the section on calculations, above),{{according to whom|date = July 2023}} and
* if it is much more than the delta-v, then, proportionally more energy is needed; if the power is limited, as with solar energy, this means that the journey takes a proportionally longer time.{{according to whom|date = July 2023}}
The second and third are the typical amounts of thrust and the typical burn times of the method; outside a gravitational potential, small amounts of thrust applied over a long period will give the same effect as large amounts of thrust over a short period, if the object is not significantly influenced by gravity.{{citation needed|date = July 2023}} The fourth is the maximum delta-v the technique can give without staging. For rocket-like propulsion systems, this is a function of mass fraction and exhaust velocity; mass fraction for rocket-like systems is usually limited by propulsion system weight and tankage weight.{{citation needed|date = July 2023}} For a system to achieve this limit, the payload may need to be a negligible percentage of the vehicle, and so the practical limit on some systems can be much lower.{{citation needed|date = July 2023}}

{| class="wikitable sortable" style="text-align:center;"
|+ Propulsion methods
! style="text-align:left;" | Method
! [[Specific impulse|Effective exhaust <br />velocity]] (km/s)
! [[Thrust]] (N)
! Firing <br />duration
! Maximum <br />[[delta-v]] (km/s)
! style="text-align:left;" | [[Technology readiness level#NASA definitions|Technology <br />readiness level]]
|-
| style="text-align:left;" | [[Solid-fuel rocket]] || {{ntsh|2.5}}<2.5 || <10<sup>7</sup> || {{Ntsh|60}}Minutes || {{Nts|7}}
| style="text-align:left;" | {{Nts|9}}: Flight proven
|-
| style="text-align:left;" | [[Hybrid rocket]] || <4 || || {{Ntsh|60}}Minutes || {{Ntsh|3}}>3
| style="text-align:left;" | {{Nts|9}}: Flight proven
|-
| style="text-align:left;" | [[Monopropellant rocket]] || {{Ntsh|2}}1–3<ref name=":0">{{Cite web|url=http://www.space-propulsion.com/brochures/hydrazine-thrusters/hydrazine-thrusters.pdf|title=Chemical monopropellant thruster family|website=Ariane Group|access-date=16 March 2019}}</ref>||{{Ntsh|{{#expr:10^.5}}}}0.1–400<ref name=":0" />||{{Ntsh|1}}Milliseconds–minutes || {{Nts|3}}
| style="text-align:left;" | {{Nts|9}}: Flight proven
|-
| style="text-align:left;" | [[Liquid-fuel rocket]] || {{ntsh|4.4}}<4.4 || <10<sup>7</sup> || {{Ntsh|60}}Minutes || {{Nts|9}}
| style="text-align:left;" | {{Nts|9}}: Flight proven
|-
| style="text-align:left;" | [[Electrostatic ion thruster]] || {{Ntsh|112.5}}15–210<ref>{{cite web| title = ESA Portal – ESA and ANU make space propulsion breakthrough|url=https://cordis.europa.eu/article/id/25070-esa-and-australian-team-develop-breakthrough-in-space-propulsion|date=18 January 2006|publisher=European Union}}</ref> || || {{Ntsh|{{#expr:3600*24*365.25*12^-.5}}}}Months–years || {{Ntsh|100}}>100
| style="text-align:left;" | {{Nts|9}}: Flight proven
|-
| style="text-align:left;" | [[Hall-effect thruster]] (HET) || {{Ntsh|29}}up to 50<ref>{{Cite web |url=https://www.grc.nasa.gov/WWW/hall/overview/overview.htm |title=Overview of Hall thrusters |access-date=2020-05-29 |archive-date=2020-05-23 |archive-url=https://web.archive.org/web/20200523031148/https://www.grc.nasa.gov/WWW/hall/overview/overview.htm }}</ref> || || {{Ntsh|{{#expr:3600*24*365.25*12^-.5}}}}Months–years || {{Ntsh|100}}>100
| style="text-align:left;" | {{Nts|9}}: Flight proven<ref>Hall-effect thrusters have been used on Russian and antecedent Soviet bloc satellites for decades.{{Original research inline|date = July 2023}}{{citation needed|date = July 2022}}</ref>
|-
| style="text-align:left;" | [[Resistojet rocket]] || {{Ntsh|4}}2–6 || {{Ntsh|{{#expr:10^-.5}}}}10<sup>−2</sup>–10 || {{Ntsh|60}}Minutes || {{dunno}}
| style="text-align:left;" | {{Nts|8}}: Flight qualified<ref>[https://www.webcitation.org/5sq1FWURx?url=http://pdf.aiaa.org/preview/CDReadyMJPC2005_1177/PV2005_4260.pdf ''A Xenon Resistojet Propulsion System for Microsatellites''] (Surrey Space Centre, University of Surrey, Guildford, Surrey)</ref>
|-
| style="text-align:left;" | [[Arcjet rocket]] || {{Ntsh|10}}4–16 || {{Ntsh|{{#expr:10^-.5}}}}10<sup>−2</sup>–10 || {{Ntsh|60}}Minutes || {{dunno}}
| style="text-align:left;" | {{Nts|8}}: Flight qualified{{Citation needed|date=February 2010}}
|-
| style="text-align:left;" | [[Field-emission electric propulsion|Field-emission<br />electric propulsion]] (FEEP) || {{Ntsh|115}}100<ref name="feep">{{cite web| url = http://www.alta-space.com/index.php?page=feep| archive-url = https://web.archive.org/web/20110707120124/http://www.alta-space.com/index.php?page=feep| archive-date = 2011-07-07| title = Alta - Space Propulsion, Systems and Services - Field Emission Electric Propulsion<!-- Bot generated title -->}}</ref>–130 || {{Ntsh|{{#expr:10^-4.5}}}}10<sup>−6</sup>–10<sup>−3</sup><ref name="feep" /> || {{Ntsh|{{#expr:3600*24*365.25*12^-.5}}}}Months–years || {{dunno}}
| style="text-align:left;" | {{Nts|8}}: Flight qualified<ref name="feep" />
|-
| style="text-align:left;" | [[Pulsed plasma thruster]] (PPT) || {{Nts|20}} || {{Nts|0.1}} || {{Ntsh|{{#expr:3600000*10^((1+ln2/ln10)/2)}}}}80–400 days || {{dunno}}
| style="text-align:left;" | {{Nts|7}}: Prototype demonstrated in space
|-
| style="text-align:left;" | [[Dual mode propulsion rocket|Dual-mode propulsion rocket]] || {{Ntsh|2.85}}1–4.7 || {{Ntsh|1000}}0.1–10<sup>7</sup> || {{Ntsh|1}}Milliseconds–minutes || {{Ntsh|6}}3–9
| style="text-align:left;" | {{Nts|7}}: Prototype demonstrated in space
|-
| style="text-align:left;" | [[Solar sail]]s
| [[Radiation pressure|{{Nts|299792.458}}]], [[Speed of light]]
| {{Ntsh|9}} 9.08/km<sup>2</sup> at 1&nbsp;[[astronomical unit|AU]]<br />908/km<sup>2</sup> at 0.1&nbsp;AU<br />10<sup>−10</sup>/km<sup>2</sup> at 4 [[Light-year|ly]]
| Indefinite
|| {{Ntsh|40}}>40
| {{Ntsh|6.9}}{{unbulleted list
 | 9: Light pressure attitude-control flight proven
 | 6: Model, 196 m<sup>2</sup> 1.12 mN 400 m/s delta-v demonstrated in interplanetary space<ref>{{cite web |url=http://www.isas.jaxa.jp/home/IKAROS-blog/?itemid=1017|title=今日の IKAROS(8/29) – Daily Report – Aug 29, 2013 | publisher=Japan Aerospace Exploration Agency (JAXA) |date=29 August 2013 | access-date=8 June 2014 |language=ja}}</ref>
 }}
|-
| style="text-align:left;" | [[Tripropellant rocket]] || {{Ntsh|3.9}}2.5–5.3{{Citation needed|date=February 2011}} || {{Ntsh|1000}}0.1–10<sup>7</sup>{{Citation needed|date=February 2011}} || {{Ntsh|60}}Minutes || {{Nts|9}}
| style="text-align:left;" | {{Nts|6}}: Prototype demonstrated on ground<ref>[http://www.astronautix.com/engines/rd701.htm RD-701<!-- Bot generated title -->] {{webarchive|url=https://web.archive.org/web/20100210203238/http://www.astronautix.com/engines/rd701.htm |date=2010-02-10 }}</ref>
|-
| style="text-align:left;" | [[Magnetoplasmadynamic thruster|Magnetoplasmadynamic<br />thruster]] (MPD) || {{Ntsh|60}}20–100 || {{Nts|100}} || {{Ntsh|{{#expr:3600*24*7}}}}Weeks || {{dunno}}
| style="text-align:left;" | {{Nts|6}}: Model, 1&nbsp;kW demonstrated in space<ref>{{cite web| url = https://translate.google.com/translate?hl=en&sl=ja&u=http://www.isas.jaxa.jp/ISASnews/No.190/labo-5.html| title = Google Translate<!-- Bot generated title -->}}</ref>
|-
| style="text-align:left;" | [[Nuclear thermal rocket|Nuclear–thermal rocket]] || {{Nts|9}}<ref name="rd0410">[http://www.astronautix.com/engines/rd0410.htm RD-0410<!-- Bot generated title -->] {{webarchive|url=https://web.archive.org/web/20090408122011/http://www.astronautix.com/engines/rd0410.htm |date=2009-04-08 }}</ref> || {{Ntsh|10000000}}10<sup>7</sup><ref name="rd0410" /> || {{Ntsh|60}}Minutes<ref name="rd0410" /> || {{Ntsh|20}}>20
| style="text-align:left;" | {{Nts|6}}: Prototype demonstrated on ground
|-
| style="text-align:left;" | Propulsive [[mass driver]]s || {{Ntsh|15}}0–30 || {{Ntsh|1000000}}10<sup>4</sup>–10<sup>8</sup> || {{Ntsh|{{#expr:3600*24*31}}}}Months || {{dunno}}
| style="text-align:left;" | {{Nts|6}}: Model, 32&nbsp;MJ demonstrated on ground
|-
| style="text-align:left;" | [[Tether propulsion]] || {{n/a}} || {{Ntsh|1000000}}1–10<sup>12</sup> || {{Ntsh|60}}Minutes || {{Ntsh|7}}7
| style="text-align:left;" | {{Nts|6}}: Model, 31.7&nbsp;km demonstrated in space<ref name="Tether">[http://www.yes2.info/ Young Engineers' Satellite 2<!-- Bot generated title -->]  {{webarchive|url=https://web.archive.org/web/20030210014335/http://www.yes2.info/ |date=2003-02-10 }}</ref>
|-
| style="text-align:left;" | [[Air-augmented rocket]] || {{Ntsh|5.5}}5–6 || {{Ntsh|1000}}0.1–10<sup>7</sup> || {{Ntsh|{{#expr:60^.5}}}}Seconds–minutes || {{Ntsh|7}}>7?
| style="text-align:left;" | {{Nts|6}}: Prototype demonstrated on ground<ref>[http://astronautix.com/lvs/gnom.htm Gnom] {{webarchive|url=https://web.archive.org/web/20100102204131/http://astronautix.com/lvs/gnom.htm |date=2010-01-02 }}</ref><ref>[http://www.grc.nasa.gov/WWW/RT2002/5000/5880trefny.html NASA GTX] {{webarchive |url=https://web.archive.org/web/20081122140310/http://www.grc.nasa.gov/WWW/RT2002/5000/5880trefny.html |date=November 22, 2008 }}</ref>
|-
| style="text-align:left;" | [[Liquid air cycle engine|Liquid-air-cycle engine]] || {{Nts|4.5}} || {{Ntsh|100000}}10<sup>3</sup>–10<sup>7</sup> || {{Ntsh|{{#expr:60^.5}}}}Seconds–minutes || {{dunno}}
| style="text-align:left;" | {{Nts|6}}: Prototype demonstrated on ground
|-
| style="text-align:left;" | [[Pulsed inductive thruster|Pulsed-inductive thruster]] (PIT) || {{Ntsh|45}}10–80<ref name="PIT">{{cite web| url = https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930023164_1993023164.pdf| title = The PIT MkV pulsed inductive thruster}}</ref> || {{Nts|20}} || {{Ntsh|{{#expr:3600*24*31}}}}Months || {{dunno}}
| style="text-align:left;" | {{Nts|5}}: Component validated in vacuum<ref name="PIT" />
|-
| style="text-align:left;" | [[Variable specific impulse magnetoplasma rocket|Variable-specific-impulse<br />magnetoplasma rocket]]<br />(VASIMR) || {{Ntsh|155}}10–300{{Citation needed|date=February 2011}} || {{Ntsh|620}}40–1,200{{Citation needed|date=February 2011}} || {{Ntsh|{{#expr:3600*24*31^.5}}}}Days–months || {{Ntsh|100}}>100
| style="text-align:left;" | {{Nts|5}}: Component, 200&nbsp;kW validated in vacuum
|-
| style="text-align:left;" | [[Magnetic field oscillating amplified thruster|Magnetic-field oscillating<br />amplified thruster]] (MOA) || {{Ntsh|70}}10–390<ref name="MOA">{{cite web| url = http://scidoc.org/articlepdfs/IJASAR/IJASAR-2470-4415-10-102.pdf| title = Thermal velocities in the plasma of a MOA Device, M.Hettmer, Int J Aeronautics Aerospace Res. 2023;10(1):297-300}}</ref> || {{Ntsh|{{#expr:10^-.5}}}}0.1–1 || {{Ntsh|{{#expr:3600*24*31^.5}}}}Days–months || {{Ntsh|100}}>100
| style="text-align:left;" | {{Nts|5}}: Component validated in vacuum
|-
| style="text-align:left;" | [[Solar thermal rocket|Solar–thermal rocket]] || {{Ntsh|9.5}}7–12 || {{Ntsh|10}}1–100 || {{Ntsh|{{#expr:3600*24*7}}}}Weeks || {{Ntsh|20}}>20
| style="text-align:left;" | {{Nts|4}}: Component validated in lab<ref>{{cite news|url=https://spaceref.com/press-release/pratt-whitney-rocketdyne-wins-22-million-contract-option-for-solar-thermal-propulsion-rocket-engine/|title= Pratt & Whitney Rocketdyne Wins $2.2 Million Contract Option for Solar Thermal Propulsion Rocket Engine|date= June 25, 2008|publisher=Pratt & Whitney [[Rocketdyne]])}}</ref>
|-
| style="text-align:left;" | [[Radioisotope rocket]]/[[World Is Not Enough (spacecraft propulsion)|Steam thruster]] || {{Ntsh|7.5}}7–8{{citation needed|date=January 2011}} || {{Ntsh|1.4}}1.3–1.5 || {{Ntsh|{{#expr:3600*24*31}}}}Months || {{dunno}}
| style="text-align:left;" | {{Nts|4}}: Component validated in lab
|-
| style="text-align:left;" | [[Nuclear electric rocket|Nuclear–electric rocket]]
| colspan=4 {{n/a|As electric propulsion method used}}
| style="text-align:left;" | {{Nts|4}}: Component, [[Safe Affordable Fission Engine|400&nbsp;kW validated in lab]]
|-
| style="text-align:left;" | [[Project Orion (nuclear propulsion)|Orion Project]] (near-term<br />nuclear pulse propulsion) || {{Ntsh|60}}20–100 || {{Ntsh|{{#expr:10^10.5}}}}10<sup>9</sup>–10<sup>12</sup><!--not a misprint--> || {{Ntsh|{{#expr:3600*24*7}}}}Days || {{Ntsh|45}}30–60
| style="text-align:left;" | {{Nts|3}}: Validated, 900&nbsp;kg proof-of-concept<ref>{{cite web| url=http://nuclearweaponarchive.org/Usa/Tests/Plumbob.html#PascalB| title=Operation Plumbbob|date=July 2003| access-date=2006-07-31}}</ref><ref>{{cite web| url=http://nuclearweaponarchive.org/Usa/Tests/Brownlee.html| title=Learning to Contain Underground Nuclear Explosions| first=Robert R.| last=Brownlee|date=June 2002| access-date=2006-07-31}}</ref>
|-
| style="text-align:left;" | [[Space elevator]] || {{n/a}} || {{n/a}} || Indefinite || {{Ntsh|12}}>12
| style="text-align:left;" | {{Nts|3}}: Validated proof-of-concept
|-
| style="text-align:left;" | [[Reaction Engines SABRE]]<ref name="SABRE" /> || {{Ntsh|17.25}}30/4.5 || {{Ntsh|1000}}0.1 – 10<sup>7</sup> || {{Ntsh|60}}Minutes || {{Nts|9.4}}
| style="text-align:left;" | {{Nts|3}}: Validated proof-of-concept
|-
| style="text-align:left;" | [[Electric sail]]s
| [[Solar wind#Emission|145–750, solar wind]]
| {{dunno}} || Indefinite || {{Ntsh|40}}>40
| style="text-align:left;" | {{Nts|3}}: Validated proof-of-concept
|-
| style="text-align:left;" | [[Magnetic sail#Magsail (MS)|Magsail]] in [[Solar wind]]|| {{n/a}} || {{Ntsh|644}}{{Nts|644}}<ref name=":AndrewsZubrin90">{{Cite journal |last1=Andrews |first1=Dana |last2=Zubrin |first2=Robert |date=1990 |title=MAGNETIC SAILS AND INTERSTELLAR TRAVEL |url=https://www.academia.edu/78476000 |journal=Journal of the British Interplanetary Society |volume=43 |pages=265–272 |via=JBIS}}</ref>{{Efn|Divided by 3.1 correction factor.<ref name=":Freeland2015" />}} || Indefinite || {{Ntsh|250}}250–750
| style="text-align:left;" | {{Nts|3}}: Validated proof-of-concept
|-
| style="text-align:left;" | [[Magnetic sail#Magnetoplasma sail (MPS)|Magnetoplasma sail]] in [[Solar wind]]<ref name=":222">{{Cite journal |last1=Funaki |first1=Ikkoh |last2=Kajimura |first2=Yoshihiro |last3=Ashida |first3=Yasumasa |last4=Yamakawa |first4=Hiroshi |last5=Nishida |first5=Hiroyuki |last6=Oshio |first6=Yuya |last7=Ueno |first7=Kazuma |last8=Shinohara |first8=Iku |last9=Yamamura |first9=Haruhito |last10=Yamagiwa |first10=Yoshiki |date=2013-07-14 |title=Magnetoplasma Sail with Equatorial Ring-current |url=https://arc.aiaa.org/doi/10.2514/6.2013-3878 |journal=49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference |series=Joint Propulsion Conferences |language=en |location=San Jose, CA |publisher=American Institute of Aeronautics and Astronautics |doi=10.2514/6.2013-3878 |isbn=978-1-62410-222-6}}</ref>|| 278 || {{Ntsh|700}}700 || {{Ntsh|{{#expr:3600*24*31}}}}Months–Years || {{Ntsh|250}}250–750
| style="text-align:left;" | {{Nts|4}}: Component validated in lab<ref name=":3">{{Citation |last1=Funaki |first1=Ikkoh |title=Solar Wind Sails |date=2012-03-21 |url=http://www.intechopen.com/books/exploring-the-solar-wind/solar-wind-sails |work=Exploring the Solar Wind |editor-last=Lazar |editor-first=Marian |publisher=InTech |language=en |bibcode=2012esw..book..439F |doi=10.5772/35673 |isbn=978-953-51-0339-4 |access-date=2022-06-13 |last2=Yamakaw |first2=Hiroshi|s2cid=55922338 |doi-access=free }}</ref>
|-
| style="text-align:left;" | [[Magnetic sail#Magsail (MS)|Magsail]] in [[Interstellar medium]]<ref name=":Freeland2015">{{Cite journal |last=Freeland |first=R.M. |date=2015 |title=Mathematics of Magsail |url=https://bis-space.com/shop/product/mathematics-of-magsails/ |journal=Journal of the British Interplanetary Society |volume=68 |pages=306–323 |via=bis-space.com}}</ref>
|{{n/a}}
|88,000 initially
|{{Ntsh|{{#expr:3600*24*365*10}}}}Decades
|{{Ntsh|15000}}15,000
| style="text-align:left;" |{{Nts|3}}: Validated proof-of-concept
|-
| style="text-align:left;" | [[Beam-powered propulsion|Beam-powered]]/[[laser propulsion|laser]]
| colspan=4 {{n/a|As propulsion method powered by beam}}
| style="text-align:left;" | {{Nts|3}}: Validated, 71&nbsp;m proof-of-concept
|-
| style="text-align:left;" | [[Launch loop]]/[[orbital ring]] || {{n/a}} || {{Ntsh|10000}}10<sup>4</sup> || {{Ntsh|60}}Minutes || {{Ntsh|20.5}}11–30
| style="text-align:left;" | {{Nts|2}}: [[Maglev (transport)|Technology]] concept formulated
|-
| style="text-align:left;" | [[Nuclear pulse propulsion]]<br />([[Project Daedalus]]' drive) || {{Ntsh|510}}20–1,000 || {{Ntsh|{{#expr:10^10.5}}}}10<sup>9</sup>–10<sup>12</sup><!--not a misprint--> || {{Ntsh|{{#expr:3600*24*365.25}}}}Years || {{Ntsh|15000}}15,000
| style="text-align:left;" | {{Nts|2}}: Technology concept formulated
|-
| style="text-align:left;" | [[Gas core reactor rocket|Gas-core reactor rocket]] || {{Ntsh|15}}10 – 20 || {{Ntsh|{{#expr:10^4.5}}}}10<sup>3</sup>–10<sup>6</sup> || {{dunno}} || {{dunno}}
| style="text-align:left;" | {{Nts|2}}: Technology concept formulated
|-
| style="text-align:left;" | [[Nuclear salt-water rocket]] || {{Nts|100}} || {{Ntsh|100000}}10<sup>3</sup>–10<sup>7</sup> || {{Ntsh|1800}}Half-hour || {{dunno}}
| style="text-align:left;" | {{Nts|2}}: Technology concept formulated
|-
| style="text-align:left;" | [[Fission sail]] || {{dunno}} || {{dunno}} || {{dunno}} || {{dunno}}
| style="text-align:left;" | {{Nts|2}}: Technology concept formulated
|-
| style="text-align:left;" | [[Fission-fragment rocket]] || {{Nts|15000}} || {{dunno}} || {{dunno}} || {{dunno}}
| style="text-align:left;" | {{Nts|2}}: Technology concept formulated
|-
| style="text-align:left;" | [[Nuclear photonic rocket|Nuclear–photonic rocket]]/[[Photon rocket]] || [[Radiation pressure|{{Nts|299792.458}}]], [[Speed of light]] || {{Ntsh|{{#expr:10^-2.5}}}}10<sup>−5</sup>–1 || {{Ntsh|{{#expr:3600*24*365.25*10^.5}}}}Years–decades || {{dunno}}
| style="text-align:left;" | {{Nts|2}}: Technology concept formulated
|-
| style="text-align:left;" | [[Fusion rocket]] || {{Ntsh|550}}100–1,000{{citation needed|date=January 2011}} || {{dunno}} || {{dunno}} || {{dunno}}
| style="text-align:left;" | {{Nts|2}}: Technology concept formulated
|-
| style="text-align:left;" | [[Antimatter-catalyzed nuclear pulse propulsion|Antimatter-catalyzed<br />nuclear pulse propulsion]] || {{Ntsh|2100}}200–4,000 || {{dunno}} || {{Ntsh|{{#expr:3600*24*7^.5}}}}Days–weeks || {{dunno}}
| style="text-align:left;" | {{Nts|2}}: Technology concept formulated
|-
| style="text-align:left;" | [[Antimatter rocket]] || {{Ntsh|55000}}10,000–100,000{{citation needed|date=January 2011}}  || {{dunno}} || {{dunno}} || {{dunno}}
| style="text-align:left;" | {{Nts|2}}: Technology concept formulated
|-
| style="text-align:left;" | [[Bussard ramjet]] || {{Ntsh|10001.1}}2.2–20,000 || {{dunno}} || Indefinite || {{Ntsh|30000}}30,000
| style="text-align:left;" | {{Nts|2}}: Technology concept formulated
|-
! style="text-align:left;" | Method
! [[Specific impulse|Effective exhaust <br />velocity]] (km/s)
! [[Thrust]] (N)
! Firing <br />duration
! Maximum <br />[[delta-v]] (km/s)
! style="text-align:left;" | [[Technology readiness level#NASA definitions|Technology <br />readiness level]]
|}
'''Table Notes'''{{Notelist}}