Re: "the monolith is a representation of a wideframe cinema screen rotated 90°."
If the engines are meant to be nuclear fission - which is what I remember from the book - then what fuel would you need, I wonder. Is it more likely to be reaction mass, than "fuel" as such?
Correct. Anything that you can pump through the reactor will do. In the book, it was ammonium, which needs pre-heating but then one does have a fission reactor nearby. Hydrogen would give best specific impulse, but it's hard to keep in the tanks.