Solar Sails

Cool post here

Solar sail technology is no idle dream. After extensive study at Marshall Space Flight Center, NASA’s basic sail design has reached the point where space testing is the logical next step even as research continues in European venues like Germany’s DLR. When we begin a serious push into solar sail technologies, we’ll need to test these designs in near-Earth orbit, and then move out into the Solar System. A logical mission for early sails will be, as Friedman notes, a replacement for the Advanced Composition Explorer (ACE), a mission nearing the end of its lifetime.

Solar Sails on Wikipedia