Continuity mistake: The gash on Kirk's right cheek disappears between the time he and McCoy fall asleep in the cave and when McCoy wakes up to find Kirk at Nona's side. (00:21:30 - 00:23:15)
Continuity mistake: When Nona is trying to seduce Kirk, we see a close-up of him with nothing on his shoulders. Cut to a two-shot and suddenly Nona's arms are over his shoulders and around his neck. (00:41:00)
Continuity mistake: In the original version, the planet is the same as the one used in "Bread and Circuses", but when the Enterprise leaves orbit at the end, it is a totally different planet, as it is the one used in "Friday's Child".
Chosen answer: If they're in orbit, they're being pulled along by the planet's gravity well, therefore, impulse engines would only be used for minor corrections and would be "on standby" while in orbit, but not active. (Like keeping your car idling without revving the engine and creating plumes of exhaust).
Captain Defenestrator
Thank you for the info.
Movie Nut