The only thing I can figure is that this beam-target fusion except that the proton beam is their primary thruster so that any protons that don't fuse are not wa

The only thing I can figure is that this beam-target fusion except that the proton beam is their primary thruster so that any protons that don't fuse are not wasted. Still not sure how they get a 50% increase from fusion with boron but I assume that is merely optimistic.