Wow... SM you are a true lateral thinker...
HI ALL
SM that's a really cool trick - using antiprotons to make W bosons. How the heck did you think of it??? Slight problem is that the W-bosons will decay pretty quickly releasing all that kinetic energy back at the ship... but it might thermalise the rads enough so they're no longer so penetrating.
Cool idea. Or rather HOT... the energy flux of the interstellar medium is really quite high. Thousands of degrees for speeds > 0.9c. Probably need a big tungsten spike as the ship's prow to handle it.
Next: I want to see you conjure up a neutrino rocket!
Adam