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

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?)