Space X released a video last Friday of a test launch for its prototype rocket, the reusable Grasshopper. The 10-story tall rocket takes off and — most impressively — lands vertically. As the video description notes:
Previous Grasshopper tests relied on the other rocket sensors but for this test, an additional, higher accuracy sensor was in the control loop. In other words, SpaceX was directly controlling the vehicle based on new sensor readings, adding a new level of accuracy in sensing the distance between Grasshopper and the ground, enabling a more precise landing.
Watching the rocket descend, perfectly stable, from more than 1,000 feet is impressive enough, but the video adds another nice whoa element, taken by a camera-equipped hexacopter hovering at just about the peak altitude Grasshopper reaches.