The Trouble With Tribbles - S2-E15
Audio problem: Near the end of the episode, Kirk asks Scotty where the Tribbles are. Scotty approaches him and says, 'I used the-' before the shot cuts to a close-up of him saying '-transporter, Captain'. In the wide shot, his mouth doesn't move. (00:48:42)






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