Of course, that never really happened: the impulse drive behaved quite unlike rockets throughout TOS.
Okay, there might have been an element of "directed thrust" to it, but that's as far as the rocket analogy ever went. There was no propellant involved, there was no mention of exhaust, and the accelerations provided were physically impossible even for the ideal rocket.
What to make of the material in novels? Some, like Gene's novelization, describe a rocket; others, like Carey's Final Frontier
, establish a field drive with similar finality. The latter makes more sense in terms of observed behavior and leaves more room for the impossibilities involved, but it remains as unaired as the former.