The Ikaros, launched back on May 21st, is safely in orbit and today Japan's space agency reports that the craft's solar sails are fully extended. The Ikaros's claim to fame is that it'll use only the sun to propel itself and continuously generate power, making it an ideal candidate for deep space missions.
The force with which Ikaros will propel itself, though, is admittedly tiny. It relies on particles of light impacting against its sail, which, all told, will apply about 7.5 microns of force against it. This force is continuous, however, and like an ion-propelled drive it should continue to pick up speed over time. It could even be considered "fast" after quite some time.
"Fast" is even the goal. After this acceleration test JAXA will know more, but the end goal is create lightweight, fast and fuel-saving ships based on the Ikaros that could explore deeper into space.