Trivia: Gene Roddenberry wanted "alien plants" for the planet's surface, but had trouble communicating the idea to the prop department. They sent dozens of lush, green potted specimens, all very terrestrial. A frustrated Roddenberry finally grabbed one potted tree, yanked it out of the soil and stuck it back in upside down with its bare, tangled roots exposed. "There," he grumped. "Now that's an alien plant!"
Trivia: For her Orion slave girl dance, Susan Oliver was painted green from head to toe. But every time production footage of her came back from the processing lab, no trace of her green make-up job showed on film. After three rounds of Gene Roddenberry ordering the make-up crew to "paint her greener!" it was finally deduced that the lab techs, assuming her color was a lighting error, had been re-tinting her a nice, healthy pink every time.
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