That is game mechanics not canon. Lets put it this way. If chief was in game how he was in the canon...there would be no game. In game you die by headshot in order to level the playing field. In game you die by a single rocket to level the playing field. The kinetic and explosive force of a heat rocket is nowhere near that of an orbital breach such as a metorite impacting earth. Masterchief has proven he can odst without a pod or protection and survive. Halo 3 for example. Master chief was a damn metor. He even burned up in the atmosphere. And what bappened? He took a nap. Then woke up. He went from knocked out to combat ready, tben combat efficient In less than ten seconds. To the point he noticed a cloaked elite and was able to move forward snag johnsons pistol and ram it into the elites mouth in about 1.5 seconds. Going off of just that alone, I believe chief would just shrug off this bfg 9000 you speak of. In the realm of physics...if that weapon was nearly as powerful as the orbital re entry chief survived the kinetic energy from the blast would obliterate not just the enemies but you as well. And no. Im no expert I physics and I am sure so.eone will point that out. However, I think you get my point.

Forces of hell > This has had an in depth comparison before, and Doom guy won as well.