Edit: Here is a video walk-through of the bunker!
https://www.youtube.com/watch?v=QFynhHBPzm4&feature=youtu.be
http://i.imgur.com/i7KJeJG.jpg
http://i.imgur.com/jOtxWlb.jpg
Here is a tutorial on how to do it.
http://www.reddit.com/r/DestinyTheGame/comments/2b80fh/hidden_area_glitch_seraphim_vault/
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I tried to do exactly what you did in your video, but first, there are two ??? guys there, and when I finally get past them and ride off the cliff, my sparrow just explodes on the water.