Abstract: Aerospike nozzles are being considered in the development of the Single Stage to Orbit launching vehicles because of their prominent features and altitude compensating characteristics. The annular nozzle, also sometimes known as the plug or "altitude-compensating" nozzle, is the least employed of those discussed due to its greater complexity. The term "annular" refers to the fact that combustion occurs along a ring, or annulus, around the base of the nozzle. "Plug" refers to the centerbody that blocks the flow from what would be the center portion of a traditional nozzle. As any fluid dynamicist recognizes, the significant disadvantage of the "flat" plug is that a turbulent wake forms aft of the base at high altitudes resulting in high base drag and reduced efficiency "Altitude-compensating" is sometimes used to describe these nozzles since that is their primary advantage, a quality that will be further explored later. . However, this problem can be greatly alleviated in an improved version of the truncated spike that introduces a "base bleed," .This paper presents the aerodynamic features performance characteristics and advantades and disadvantages