Why the Different Engine Sizes?

Watching season 5 of SGA. Why does the Daedalus have different engine sizes? I would get it if one size was for sublight and the other for hyperdrive, but we see all engines firing when they are traveling at sublight.

Is there an in-universe explanation, or is it just "many engines looks cool"?

Watching season 5 of SGA. Why does the Daedalus have different engine sizes? I would get it if one size was for sublight and the other for hyperdrive, but we see all engines firing when they are traveling at sublight.

Is there an in-universe explanation, or is it just "many engines looks cool"?