IKAROS Uses "Smart Glass" For Steering.
AIAA Daily Launch 28JUL2010

New Scientist (7/27, Courtland) (http://mailview.custombriefings.com/mailview.aspx?m=2010072801aiaa&r=4921837-0343&l=01b-713&t=c) magazine reported, "Japan's IKAROS spacecraft has used 'smart glass' technology to steer using only the pressure of sunlight – a first for solar sails." The sail used "liquid crystal devices along the outer edge" to steer by adjusting the "reflectivity of the outer sections of the sail; switching one on creates a mirror-like effect, allowing sunlight to push more on those parts of the sail." However, JAXA's Yuichi Tsuda noted that this is not a fast process when compared to thrusters and "it gets less effective the faster the sail spins."