On: SpaceX Grasshopper Flies High

[JshWright]

I assume it's some sort of gimbal control/vectoring of the thrust (since I don't see any 'extra' exhaust further up the rocket)

[rst → JshWright]

It gimbals the engine for pitch and yaw, and uses cold-gas thrusters for roll (around the vertical axis).

[savrajsingh → JshWright]

Yeah I think that's what it is unless told otherwise. Quite impressive stuff!