Editing Magnetohydrodynamic drive (section)

===Spacecraft propulsion===

{{main|Plasma propulsion engine}}
{{See also|Magnetoplasmadynamic thruster|Pulsed inductive thruster}}
A number of experimental methods of [[spacecraft propulsion]] are based on magnetohydrodynamics. As this kind of MHD propulsion involves compressible fluids in the form of plasmas (ionized gases) it is also referred to as magnetogasdynamics or '''magnetoplasmadynamics'''.

In such [[Electrically powered spacecraft propulsion#Electromagnetic|electromagnetic thrusters]], the working fluid is most of the time ionized [[hydrazine]], [[xenon]] or [[lithium]]. Depending on the propellant used, it can be seeded with [[alkali]] such as [[potassium]] or [[caesium]] to improve its electrical conductivity. All charged species within the plasma, from positive and negative ions to free electrons, as well as neutral atoms by the effect of collisions, are accelerated in the same direction by the Lorentz "body" force, which results from the combination of a magnetic field with an orthogonal electric field (hence the name of "cross-field accelerator"), these fields not being in the direction of the acceleration. This is a fundamental difference with [[ion thruster]]s which rely on [[electrostatics]] to accelerate only positive ions using the [[Coulomb force]] along a [[high voltage]] electric field.

First experimental studies involving cross-field plasma accelerators (square channels and rocket nozzles) date back to the late 1950s. Such systems provide greater [[thrust]] and higher [[specific impulse]] than conventional [[Rocket engine#Terminology|chemical rockets]] and even modern ion drives, at the cost of a higher required energy density.<ref name="Resler 1958">{{cite journal
 |last1=Resler |first1=E.L.
 |last2=Sears |first2=W.R.
 |title=Magneto-Gasdynamic Channel Flow
 |date=1958
 |journal=Zeitschrift für Angewandte Mathematik und Physik
 |volume=9b
 |issue=5–6
 |pages=509–518
|doi=10.1007/BF02424770
 |bibcode=1958ZaMP....9..509R
 |s2cid=97266881
 }}</ref><ref name="Wilson 1958">{{cite book
 |last1=Wilson |first1=T.A.
 |chapter=Remarks on Rocket and Aerodynamic Applications of Magnetohydrodynamic Channel Flow
 |date=December 1958
 |publisher=Cornell University
 |title=TN-58-1058, ASTIA 207 228
}}</ref><ref name="Wood 1960">{{cite journal
 |last1=Wood |first1=G.P.
 |last2=Carter |first2=A.F.
 |title=Considerations in the Design of a Steady D.C. Plasma Generator
 |date=1960
 |journal=Dynamics of Conducting Gases (Proceedings of the 3rd Biennial Gas Dynamics Symposium)
 }}</ref><ref name="Kerrebrock 1960">{{cite journal
 |last1=Kerrebrock |first1=Jack L.
 |title=Electrode Boundary Layers in Direct-Current Plasma Accelerators
 |date=August 1961
 |journal=Journal of the Aerospace Sciences
 |volume=28
 |issue=8
 |pages=631–644
 |url=http://ayuba.fr/pdf/kerrebrock1961.pdf
 |doi=10.2514/8.9117
}}</ref><ref name="Oates 1962">{{cite journal
 |last1=Oates |first1=Gordon C.
 |title=Constant-Electric-Field and Constant-Magnetic-Field Magnetogasdynamic Channel Flow
 |date=1962
 |journal=Journal of the Aerospace Sciences
 |volume=29
 |issue=2
 |pages=231–232
 |doi=10.2514/8.9372
 |url=http://ayuba.fr/pdf/oates1962.pdf
 }}</ref><ref name="Rosciszewski 1965">{{cite journal 
 |last1=Rosciszewski |first1=Jan
 |title=Rocket motor with electric accelerationin tehthroat
 |date=March 1965
 |journal=Journal of Spacecraft and Rockets
 |volume=2
 |issue=2
 |pages=278–280
 |url=http://ayuba.fr/pdf/rosciszewski1965.pdf
 |doi=10.2514/3.28172
|bibcode=1965JSpRo...2..278R}}</ref>

Some devices also studied nowadays besides cross-field accelerators include the [[magnetoplasmadynamic thruster]] sometimes referred to as the Lorentz force accelerator (LFA), and the electrodeless [[pulsed inductive thruster]] (PIT).

Even today, these systems are not ready to be launched in space as they still lack a suitable compact power source offering enough [[energy density]] (such as hypothetical [[Fusion power|fusion reactors]]) to feed the power-greedy [[electromagnet]]s, especially pulsed inductive ones. The rapid ablation of electrodes under the intense thermal flow is also a concern. For these reasons, studies remain largely theoretical and experiments are still conducted in the laboratory, although over 60 years have passed since the first research in this kind of thrusters.