Cleaning Up Space Debris

Lasers and Water Guns.

Using aging rockets loaded with water to spray orbiting junk. His idea is that the extraterrestrial shower would gradually knock refuse down toward the atmosphere, where it would burn up, as would the launcher. The water would turn to steam.

Johns Hopkins University's Applied Physics Laboratory, a leading space research center, recently conducted feasibility studies into junk-zapping lasers and garbage-collecting rockets

Source