I'm guessing it refers to the problem when docking the shuttle or other spacecraft of making sure that thruster exhaust is never directed towards the station itself. I remember seeing a video that showed the shuttle approaching the station on a nautilus-shell sort of trajectory, so that thruster fire was always directed out and away from the station.
Apart from the obvious danger of impact from ice and other debris from thrusters, unburnt hydrazine is nasty stuff- you don't want to deposit any on the station, only to have an astronaut on EVA scrape some off by accident and bring it back inside.
Apart from the obvious danger of impact from ice and other debris from thrusters, unburnt hydrazine is nasty stuff- you don't want to deposit any on the station, only to have an astronaut on EVA scrape some off by accident and bring it back inside.