I wanted to know whether or not a perfect mirror would experience recoil when light reflects off it, and I also wanted to know whether or not light can cause a recoil during total internal reflection. I suspect that the recoil is negligible (Even with a normal mirror) and that you could easily make a reaction-less drive for a spacecraft by simply firing a high powered laser at a mirror at the back of the spacecraft so that the light reflects back and hits the front. The laser will recoil, pushing the craft forward and the reflected light will also push it forward. This seems to violate conservation of momentum. Though it would take alot of energy to use for useful effect.