There are a lot of grammatical errors and flaws in your text. I will however not concentrate on those (except for the one below because that really should be fixed).
Quote: "...tall enough to house a sex story building was before me."
I enjoyed reading it, your pacing is good, your descriptions of things is minimal but I was still able to create a good picture in my mind of what was going on.
The jokes you try to make, for instance the 3 headed rat, seem to come out of nowhere. I can't imagine the captain saying something like that in the situation you described. If you're trying to work on his personality then that's fine, maybe he is a captain that likes cracking weird jokes, there's no problem with that. But please, keep it to the captain if that's what you're aiming for. In your text the jokes came from different crew members every time, which just makes it more chaotic to understand the people I'm reading about.
How did the captain know that Mr Reid was helping Miller? Does the captain have psychotic powers? Does he have a tracking device on Mr Reid? You never explain that part.
I think a big problem with your text is the fact that all of the personalities are very generic. You need to add more distinction. You fail to describe enough of their emotions. Mr Reid should be terrified when he peaked up the vent, yet I didn't get that impression. Mr Reid seemed very casual when the monster was trying to knock down the door. He even went up to the door and tapped it, is that really what he would do in that situation? I had no idea how he was feeling during all of that. I'm not saying that it was wrong of him to tap the door, you just need to explain his personality further for me to believe that he'd do something like that. Perhaps describe him as a fearless daredevil? Pump him up with manliness, give him a cigar or something, anything to make him awesome so he would be the guy that would tap a door being broken down by a huge monster and not be the guy that would run away screaming like a pussy.
The doc could explain what he's doing with the highest medical precision. You could make him speak with the highest form of English or something, because he'd be the person with the most knowledge under his belt.
The captain in my mind would be this fearless leader, but still has sympathy and feelings for his crew members. Maybe give him something cool like a fake eye that shoots lasers. You don't have to do that, that's just my imagination going wild right now. But he needs something that defines him.
Enough of my rambling, keep writing it.
TheComet