Field propulsion

Field propulsion is the concept of spacecraft propulsion where no propellant is necessary but instead momentum of the spacecraft is changed by an interaction of the spacecraft with external force fields, such as gravitational and magnetic fields from stars and planets. It is purely speculative and has not yet been demonstrated to be of practical use or theoretically valid.

Although not presently in wide use for space, there exist proven terrestrial examples of "Field Propulsion", in which electromagnetic fields act upon a conducting medium such as seawater or plasma for propulsion, is known as magnetohydrodynamics or MHD. MHD is similar in operation to electric motors, however rather than using moving parts or metal conductors, fluid or plasma conductors are employed. The EMS-1 and more recently the Yamato 1 are examples of such electromagnetic Field propulsion systems, first proposed in patent US 5333444 . There is definitely potential to apply MHD to the space environment and experiments such as the NASA's electrodynamic tether, Lorentz Actuated Orbits, the wingless electromagnetic air vehicle, and magnetoplasmadynamic thruster (which does use propellant) lay a solid foundation for using "fields" to propel spacecraft without propellant and standard concepts of chemical thrust. Since electrodynamics is well proven science, electromagnetic fields themselves carry momentum (see the Nichols radiometer), and electromagnetic field propulsion is not limited to the ejection velocity of particle propellants these new concepts offer tremendous potential as a future space propulsion system. They represent a radical departure from current ideas of aeronautics and rocket propulsion, and as such are controversial, but field propulsion may offer the radical breakthroughs in performance capabilities required for deep space exploration. The main limiting factors appear to the generation of the significant amounts of electrical power required and a method of strongly coupling the fields to large volumes.

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