[Steely Tom]

Good news, but I’m having a hard time understanding why one would want to dial the specific impulse to any value other than “maximum.”

[wastoute]

Where are the DiLithium crystals?

[MirrorField]

Good news, but I’m having a hard time understanding why one would want to dial the specific impulse to any value other than “maximum.”

Because sometimes you may want to trade specific impulse for increased maximum thrust. Afterburner's an awful fuel hog and you don't use it all the time, but there are situations when it's useful.