Another explanation for the EM Drive experimental findings based on a theory that allows electromagnetic fields to modify the space-time metric of General Relativity:

http://inspirehep.net/record/1220790/files/arXiv%3A1302.5690.pdfhttp://arxiv.org/pdf/1310.5029.pdf"Some axisymmetric electromagnetic modes of a truncated conical cavity are then presented

and used as source in the weak-field approximation of the equations, previously obtained,

to determine the force on the cavity. It is found that a coupling of the same magnitude

as used in [5] between the scalar and the electromagnetic field results in a correct

magnitude and sign for the forces reported in asymmetric resonant cavities. ...The theory, however, does not seem to be completely satisfactory because in its linearized version it also predicts strong gravitational effects

by the Earth’s magnetic field, which are clearly not observed. A possible resolution of

this problem is considered in the last section."

"It was shown that the weak field approximation of a rather general scalar-tensor theory of

gravity, which includes an additional scalar with strong coupling to the electromagnetic

field, as proposed in[5], could account for the forces reported on asymmetric resonant

cavities. Although highly speculative, it is interesting that this was done using the

same coupling coefficient adjusted by[5] to explain discordant measurements of Newton

gravitational constant. It is also of interest that the inclusion of the external scalar

can help to reconcile the Solar System tests with values of the Brans-Dicke parameter

close to unity (see relation (15)). The weakest part of the theory seems to be that

there is no clear way of preventing large gravitational effects due to the magnetic field

of the Earth, as predicted by Eq. (17). A possible solution can be sought in non-linear

effects,...Note that if this is possible for a static magnetic field, it could possibly not be the

case for a static electric field outside its sources, because the difference of sign would not allow real solutions.

It is so expected that static magnetic and electric fields show no unusual

gravitational effects, while

**non-stationary electromagnetic fields do**. "