Ok, I'll start a new thread, give me some time, I have to assemble things. As for the danger posed by all-solids booster, I doubt that a choke of powder grain could have provoked an all-booster explosion. Liquids, expecially involving hydrogen, are more dangerous. Anyway, the real danger is to the crew. NASA run a score of studies of effects of explosions on the launch pad by large boosters, and Apollo in particular was object of at least three studies. In the Apollo specifications there was a provision for a strong structural resistance to a launch pad explosion. The research in big solids was in part driven by safety consideration (and cost, and logistics).