The issue is that an aerospike engine is a spike engine that has been truncated, with the truncated portion replaced with an aerodynamic "spike," which also eliminates base drag.
Is it even practically possible to have a non-truncated spike engine? If you don't truncate the spike, won't it get so thin that it'd just burn/melt off? It seems like all spike engines are truncated to at least a minimal degree.
Or is the matter whether or not the truncation has aerodynamic effects? (Do any truncations not?)
