A good idea and great atmosphere, but I didn't get far because of the deaths without any warning at the start. I'd be reading a message and it would suddenly say MIA and I'd have to start again. That's really frustrating! Either give a warning, or a chance to survive, or at least a clue what to do after the first death. Still, there is a lot of potential here. :-)
(This one didn't work in Linux, just as a point for Linux users.)
Yep, it was the first door! Your approach sounds interesting, but maybe some hint to the player that they will die if they respond? Even after dying I had no idea that was the cause! Is there some in-game reason that could be worked out, as to why answering a radio immediately kills you? You could then give a hint at that after death. Just thinking of how you can make sure players don't give up at that point. :-) It's a really ominous-seeming scenario, so it would be good to make sure they experience the full thing. Good luck!
