It is unsafe to turn on the full engines of a shuttlepod below 50 kilometers' altitude... and believable that a 100 kilometer radius scorched area could be cleared by the plasma backblast of a shuttlepod's engines in "Shockwave." A shuttlepod has two plasma ducts.
"Singularity" - the Enterprise flies within 2 million kilometers of a black hole, part of a trinary system of blue giants.
"Doctor's Orders" - 10 weeks at full impulse will travel at least a quarter light year. This is noticably faster than light speed, curiously enough.