A normal ballistic missile submarine has one pressure hull, with a large section of ballistic missiles taking up the middle of it. This submarine has two pressure hulls, on either side containing no missiles, but sandwiching the missiles between them. In theory this means that you can torpedo the sub from a side, and the missiles are still okay. But it also means that the sub has ludicrous amounts of space available. No missiles taking up pressure hull space, and two, not one pressure hulls. So everything on this sub got to be more spacious and there was room for extras.

Yeah, the Typhoon sub was like two submarines side-by-side inside the external shell. The scene in the movie where Alec Baldwin fights the KGB agent between the missile silos ("Some things there don't react well to bullets") couldn't have happened as the missile tubes are between those internal hulls, though one could have argued this sub was built differently with it's "silent drive".

Still an amazing movie.

Diagram here: https://imageio.forbes.com/specials-images/imageserve/5f40d7...