The Grasshopper, developed by private company SpaceX, flew on December 17th.
Grasshopper, a space launch platform under development by SpaceX, successfully flew to a height of 131 feet (40 meters) and landed again, nearly eight times its previous test record of 5.4 meters. Grasshopper is a vertical takeoff and landing vehicle, and would be the first truly reusable space delivery system when completed. Prior spacecraft have always included sections which were permanently lost or damaged after use. Grasshopper would move to orbit, deploy its cargo, and then turn around. The rocket would boost back to earth before reorienting, deploying landing gear, and settling down. The rocket's hovering behavior is possible due to very close control of the throttle and a closed loop thrust vector.
A closed loop and throttle control system reads the outside conditions of the rocket, such as wind speed and direction, in order to maintain the rocket on a constant course while it is hovering.
Grasshopper is composed of SpaceX's Falcon 9 rocket, Merlin 1D engine, and a steel support structure with attached landing legs. Over the next several months, SpaceX will be continuing testing on the Grasshopper, building up to a successful orbital launch and re-entry. Testing on the Grasshopper has been ongoing since September.