A dumb question (or maybe not) ...

[Hotfoot]

Oddly enough, I was just playing around with this myself in the game, and I have come to the following conclusion on the matter:

Whatever mix of engines you put on a ship, you will get the worst possible bonus out of all of them. So if you have five Quantum Engines and one Ion Engine, your total movement will be 6. Remove the Ion Engine, and your speed will be 8. With a Contra-Terrene Engine in place of the Ion Engine, your speed will be 7. Use a Jacketed Photon Engine and five Quantum Engines, and your speed will be 8. Use six Quantum Engines, and your speed is 9.

Is this realistic? Perhaps not, but the way the game works, the first engine you put on a ship generates 1+b thrust, where b is the bonus thrust generated by the engine. Put one Quantum Engine on a ship, and you have a speed of 4. Each engine beyond that only adds +1 to the total movement of the ship. My guess is that it was done this way so as to allow for a much more gradual increase in ship speed, rather than automatically doubling it every significant level. I'm not certain how the modders who did quasi-newtonian movement went about it, but mixing and matching engines there might make more sense than here.

However, the only real reason I can think of to mix and match engines on a ship design is to save money, as those higher level engines tend to get expensive. While it might make sense on one level to try and boost a ship's speed just a little with one additional high-powered engine, it shouldn't make much of a difference in the normal game, since it only goes up +1 per level. If all you had to do was add one higher level engine to get the increase, we'd be seeing ships with a single Quantum Engine and five Ion Engines, which is kind of silly, in my opinion.

I won't try to rationalize it as being logical, "realistic", or whatever, it's most likely just game balance.

Now, back to dealing with those annoying Jraenar...