So I have a ship with 25 of those LV-N atomic rocket engines. Here is a picture of it. It's got a total delta v of like 16000 m/s. That big array of engines is separated into 3 stages. However, I was trying to find a way to get that 16 km/s of delta v into one stage. When I just merge all the engines into ONE STAGE, it says I only have 7km/s of delta v. WHY?!? They all have the same isp! Each engine has it's own fuel tank. All the fuel tanks are exactly the same size. How can combining a bunch of these together be less efficient than only using some of them at the same time?