Elon Musk's list of crazy/brilliant inventions is getting pretty lengthy, but he's decided to add to the list with the Saturday afternoon unveiling of "X-wing config" wings for the Falcon 9 rocket, and a self-piloting ship to act as a landing pad for the reusable rockets.
The grid fins are the small waffle-shaped wings you see on the Falcon 9 above. They give the rocket an aerodynamic surface that can be used to control the vehicle during its reentry into the atmosphere, and steer it into the right position to relight its main engine, and land on target. They're also retractable, so don't add significant drag to the rocket while it's serving its primary function of getting stuff into space.
Once the rocket is on the return leg, Musk's second announcement of the day comes into play:
In a later tweet, Musk said that the width is 300ft by 100ft, with extra wings that extend the width to 170ft. Combined with technology to keep the platform stable, that should provide a good landing platform for the rockets, whilst also being a long, long way away from other people in case things don't go quite to plan. [Twitter via TechCrunch]