Book 2 second edition makes the X-boat in Traders and Gunboats a broken design, it has to include a powerplant, and let's not mention the Annic Nova
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I think the powerplant/maneuver drive in first edition book 2 always suggested to me some sort of reaction drive, especially when it gives the number of combat turns (288=48 hours) the m-drive can be used with a full fuel tank.
Perhaps the maneuver drive generates an inertial mass reduction field around the volume of the ship (this could explain its' radiation blocking properties as well [img]graemlins/file_23.gif[/img] ) and a small fusion rocket is then used for thrust, hence you design a maneuver drive for a volume and not a mass. Too big a rocket for the field and it breaks down.