First Contact: Impulse Quads

How many impulse rockets/engines would one need on star ship?  I'm going to say 8 quads of primary impulse engines, for a total of 32 impulse engines and 32 impulse rockets. We're defining the difference as sustained power (engines) to burst power (rockets). They are also going to be more build into the hull so they can be maintained largely from inside the ship.
Larger than the Apollo (obviously) and doubled up front to back for better maneuverability.