In the final mission of Halo 3 (Halo) the Chief prematurely fires Installation 04B, destroying the Halo, the Ark, etc. shouldn't he have died, though, immediately after firing the ring? How did he survive?
Remember that, in the post-credits scene, Cortana said to Master Chief:
We made it to the portal just as it collapsed.
So what I think happened here is that the explosion somehow changed the portal's behavior sending the ship's part where Master Chief and Cortana was to one way, and the other part where the arbiter was to another way. But yes, Master Chief was very lucky.