The Corbomite Maneuver - S1-E11
Visible crew/equipment: After the Fesarius destroys the recorder marker, when Balok declares that Enterprise must also be destroyed, in the next wide shot there's a tape mark on the floor near Bailey, and another one in front of Kirk's feet. (00:21:50)
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