Generic EM Drive Information

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This is a location for assorted information concerning EM Drives. Likely applies to all current experimental efforts.

Simulating With MEEP[edit]

MEEP is is a free finite-difference time-domain (FDTD) simulation software package developed at MIT to model electromagnetic systems[1]. A number of people, including @aero, have been using it to simulate the evolution of the fields within the EM Drive.

Conservation of Energy and Momentum[edit]

See Energy Conservation and Momentum Conservation for discussions of the implications to these principles.

Mode Shape[edit]

See calculations pertaining to the relationship between thrust and mode shape at Notsosureofit's post and Rodal's response.

An EM Drive is a cavity resonator that uses the Quality Factor Q to achieve greater response. There is definitely a peak resonant frequency to achieve the highest Q, though besides Q and frequency, mode shape must also be considered. The shape of the electric and magnetic fields inside the cavity at a given frequency.[2]

The natural frequencies (and therefore the mode shapes) of a cavity are sensitive to the dimensions of the cavity. [3] A dielectric insert lowers the natural frequency at which a given mode shape takes place.[4] Here is a plot of what a few mode shapes in a cylindrical cavity look like when viewed perpendicular to the circular cross section plane.


  1. [1]
  2. Rodal on frequency, Q, and mode shape.
  3. [2]Rodal's post on geometric relations to mode shape.
  4. Rodal on the dielectric's contribution to mode shape.