Evanescent waves

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As first proposed by Aero and later refined by Rodal on the NSF forums, this theory proposes the EmDrive's tapered conical design causes a gradient in the electric field generated by the Rf source. As the EM waves inside the fustrum travel toward the small end, they are attenuated by the constricting geometry, producing evanescent waves that carry momentum. The device must then move to preserve conservation of momentum.[1]

Status

Numerical Analysis

@Aero performed calculations for evanescent waves leaking from the EM Drive and producing an external near-field. He used a two-dimensional MEEP Finite Difference model that modeled the EM Drive as a perfectly flat trapezium. Maxwell's equations were solved in the 2-D domain. The 2-D model was due to the enormous amount of memory and computer time required by the Finite Difference method, which made a 3-D model in a home PC impossible. The results from the 2-D analysis showed an efficiency rating 2-3 times that of a perfectly collimated photon drive, which is beneath the reported measurements of EM Drive by NASA Eagleworks, Shawyer's SPR and Prof. Juan Yang's team at NWPU.[2]

Utilizing MEEP 2-D model, the conclusion was that due to rapid dropoff at the frustum surface, evanescent waves were of insufficient magnitude to explain the observed thrust.[3]. See details about @aero's MEEP control file.

Relevant Papers

References