The drive's first function is to tear a hole in the fabric of space. The hole is precisely created and the ship naturally falls into the breach on a carefully
directed vector. The drive then directs some of its energy to sewing up that hole again. The act of closing the hole severs the ship's ties with normal space and allows it to begin its jump.
Is not in any way mutually exclusive with 'inflating the bubble' explanations:
~ I 'punch a hole' in space time - creating a pocket universe with a narrow 'neck' into our universe (imagine stretching a little divot into a rubber sheet).
~ I 'inflate' it by filling it full of hydrogen at suitably high energy and pressure, creating something akin to the early universe inflation (this lasted from 10^-36 to 10^-33 seconds after the big bang, so a quick process!) to create a 'universe' big enough to drive the hull of a Type S inside
~ I drive inside through the 'neck', 'breach', 'portal' or whatever you want to call it - the interface between the deformed out region and the rest of space time
~ the drive seals the 'neck'. I am now floating in a 'bubble universe' which is independent of the rest of space, and can zip off at whatever velocity the process of creating it imparted, until it falls back into contact with 'normal' space time, and opens up again somewhere (hopefully) near my destination.