[kuschku]

Actually, there are several in-universe articles saying otherwise:

The interaction between the shields and a conventional propulsive system would be horrible (you’d get fried in your own plasma).

Therefore the Interacting Magnetic Pulse system (sorry, I’m translating back here, so I dunno if that’s the correct term in the correct in-universe article in english) actually uses some weird interaction of microwaves to create "gravitational waves on which the ship then rides", as one engineer said poetically.