Aerospike engine
The aerospike engine is a type of rocket engine that maintains its aerodynamic efficiency across a wide range of altitudes. It belongs to the class of altitude compensating nozzle engines. Aerospike engines were proposed for many single-stage-to-orbit (SSTO) designs. They were a contender for the Space Shuttle main engine. However, as of 2023 no such engine was in commercial production, although some large-scale aerospikes were in testing phases.The term aerospike was originally used for a truncated plug nozzle with a rough conical taper and some gas injection, forming an "air spike" to help make up for the absence of the plug tail.