IT’S the trailblazer of solar sailing. Japan’s IKAROS spacecraft has used “smart glass” technology to steer using only the pressure of sunlight – a first for solar sails.

IKAROS launched in May and soon after became the first solar sail to be fully propelled by sunlight. Now liquid crystal devices along the outer edge of the sail have been used to steer the craft. The devices control 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.

“With this we can control both the orbit and the attitude using only …