Roton SSTO
The Roton was a single-stage-to-orbit (SSTO) concept spacecraft designed by Gary Hudson and built by Rotary Rockets Inc.The vehicle was unique in using helicopter-style rotors for landing, rather than wings or parachutes. The rotors were powered by blade-tip rockets. It was also originally intended to use a unique rotating annular aerospike engine; the engine would spin at high speed within the spacecraft to pump fuel and oxidizer through its nozzles by centrifugal force.
An atmospheric test vehicle was built which successfully flew, proving the rocket-rotor concept, but shortly afterwards the venture ran out of funds and closed down.