Was doing this again today, trying to do a Mousepath (unrelated) and stumbled across this.
It was the "clear the orion drydocks" mission, I think it was Pico? Beytan? I don't recall.
Anyway, I clicked one of the drydocks before I had come into weapons range of the first two corvettes, hit my high yield torpedo skill, and it was just letting me fire over and over again, with no effect on the drydock's health.
When I finally came into contact with the corvettes, destroyed them, and started back on the drydocks, I was bringing their health down, but when I fired without high yield, two torpedos appeared to fire (although the drydocks were only getting one set of damage), and with high yield on, it fired two as normal and the docks recieved two sets of damage.
I may be nitpicking, but I was certainly confused for the first 30 or so seconds before I decided to destroy the corvettes guarding it before taking out the drydocks.