I’ve published a paper showing mathematically how MiHsC predicts the emdrive (see the reference below), but the struggle is to convince people with an explanation that takes them from what’s known & solid and guides them into this new area. This is one of the, possibly flawed, ways I use to explain it to myself. Starting from the known: the Casimir effect is well tested (see below left). If you put two conducting plates (the black lines) close together, these damp the zero point field (orange wiggles) between them, more virtual particles hit the plates from outside then from inside & the plates move together (red arrows).
It has also been noted, this time in fluid dynamics that if you subject a boomerang-shape to random perturbations (the middle diagram above) then it also has a shadow-zone for waves between its arms, and in this case the waves push it rightwards, since the waves put inwards (and rightwards) on the arms, but there are no waves to push from inside out (and leftwards) (eg: Chakrabarty et al., 2013). Now, imagine the reverse, where you have the same boomerang shape, but the random field is more intense inside (see the right hand diagram above). This is like the emdrive whose internal em field is high. By symmetry, the boomerang now moves towards its narrow end. We’re getting close.
The MiHsC explanation of emdrive is in a similar line but the derivation is more difficult because there’s no open end now. MiHsC says that the zero point field can be made to vary in space by setting up horizons (these can be real Casimir plates or abstract information horizons). In the emdrive then the supercharged zero point field in the copper cone is more energetic at the wide end (see diagram below, note the waveforms shown are cartoons only). There is now a gradient in it from which work can be extracted, just as the Casimir effect gets energy to move from the gradient it creates in the zero point field.
One way to work out the effect of MiHsC on the emdrive is to consider the photons resonating within it. On moving towards the wide end of the cone, the photons are moving to a more energetic zero point field and so gain inertial mass due to MiHsC (yes, light has inertial mass, the Japanese have just tested a light sail: IKAROS). Going the other way the photons lose mass. The almighty cosmic accountant says "Oh dear! Net mass is going towards the right, so I'd better conserve momentum & move the emdrive to the left. Make it so!". In this new way MiHsC predicts the observed emdrive thrust quite well. As shown in the bar chart below which shows the thrust data (the purple bars) from the eight emdrive experiments so far, and the MiHsC prediction in red. For the details, see my paper below.
Chakrabarty, A. Konya, A., Wang, F., Selinger, J.V., Sun K., Wie, .H., 2013. Brownian motion of boomerang colloidal particles. Phys. Rev. Lett., 111, 160603.
McCulloch, M.E., 2015. Testing quantised inertia on the emdrive. EPL, 111, 60005. PDF