Let That Be Your Last Battlefield - S3-E15
Other mistake: At the end of the episode, as Lokai is running through the ship, his hands are empty. However, in one closeup shot he is holding onto a rope with his left hand. The rope is gone in the following shot. Presumably this rope was used to tether him to the camera as he ran so that he could maintain distance from the camera.
Let That Be Your Last Battlefield - S3-E15
Other mistake: When preparing to go around again, Sulu and Checkov start working their controls. When there is a close up of Sulu's hand, it's obviously a re-used shot of Kirk's hand starting the 30 second count down timer on the Constellation in "The Doomsday Machine" (S2 E6).
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