I just destroyed the Institute with the help of the Minutemen and am now getting tired of seeing the Prydwen in the sky. I've read on this forum that the Brotherhood can attack the castle, thus triggering the quest where you destroy them with artillery. Does anyone know specifically what triggers this? As of now the knights are all complaining that they weren't the ones who blew up the Institute, and Elder Maxson dismisses me saying he's busy, but they aren't hostile.