We currently have a lot of technology to spot objects in space. As cli already pointed out there is the heat signature of any ship. Combined with radar it shoul

We currently have a lot of technology to spot objects in space. As cli already pointed out there is the heat signature of any ship. Combined with radar it should be easy to detect ships from far away. In open space there is (probably) also no stable debris you could use. Asteroid belts are actual nothing like in the movies. There is a much bigger distance between each asteroid in the belt. http://www.scienceadviser.net/2009/09/asteroid-belt-not-as-dense-as.html http://www.scienceadviser.net/2009/09/asteroid-belt-not-as-d... Maybe the ring of a planet would work. But then the ship is at risk of being damaged by the ice and other things in the ring. And of course there are only few planetary rings compared to the rest of space.