[Type] Turborocket [Advantages] Very close to existing designs, operates in very high altitude, wide range of altitude and airspeed [Disadvantages] Atmospheric airspeed limited to same range as turbojet engine, carrying oxidiser like LOX can be dangerous. Much heavier than simple rockets. [Description] 
A combined cycle turbojet/rocket where an additional oxidiser such as oxygen is added to the airstream to increase maximum altitude