(Video Link)

While spending only $5 for the necessary modifications, Douglas Desrochers gave a rocket helicopter blades which it could use to make a smooth descent:

The HeliRocket is propelled by a standard model-rocket engine, but instead of the engine’s ejection charge deploying a parachute, it releases the rocket’s 3 tail fins. The fins then swing up into a helicopter blade configuration, which slows the rocket’s descent by converting much of its kinetic energy into drag and angular momentum (spin).

Link via CrunchGear