Magnetohydrodynamic drive
（重定向自Caterpillar drive）
![Yamato 1 on display in Kobe, Japan. The first known working prototype.](/Images/godic/202501/03/Yamato1_12209.jpg")
![The front of Yamato 1](/Images/godic/202501/03/Yamato_1_from_the_front2209.JPG")
![An MHD thruster from the boat, at the Ship Science Museum in Tokyo.](/Images/godic/202501/03/Yamato_1_thruster2209.jpg")
![A view through a tube in the thruster off Yamato I, at the Ship Science Museum in Tokyo. The electrode plates are visible top and bottom](/Images/godic/202501/03/Magnetohydrodynamic_drive_tube2209.jpg")
A magnetohydrodynamic drive or MHD propulsor is a method for propelling vessels using only electric and magnetic fields with no moving parts, using magnetohydrodynamics.
The working principle involves electrification of the propellant (gas or water) which can then be directed by a magnetic field, pushing the vehicle in the opposite direction. Although some working prototypes exist, MHD drives remain impractical .