From The Crop Circle Ship Wiki
(Note: This is only an extremely rough representation.)
Below, the Hydrogen Container may also be marked as HC and the Magnetron may be marked as M.
Note that the Hydrogen Container is often shown as cone shaped.
 An interesting email
Jeremy, The magnetron needs to be in a negative pressure environment. When operates, it creates a force field around itself, like a void. It just has the ability to stay put wherever you want it. You force the hydrogen through the magnetron, thereby creating drive, direction is created by slide (turning at an angle) of triangular magnets that oppose the inner wheel. (also triangular magnets that turn and oppose the outside rim. In the grand scheme of things this device creates the engine to go through space and bounce any atoms away from itself. There is a vacuum that is created molecularly at the rear so as to push but only in theory. I'll try to dig out my drawings, after I would awake, I would write down what I remembered.
 Also see