A spike isn't the only way to compensate for altitude, it's just the most popularized one. There are also expansion-deflection nozzles, expanding nozzles and notably removable inserts for ordinary bell nozzles, which are simple, good enough and are being used on real rockets for a long time.

> But all in all, I think the best way I can summarize the Aerospike is to compare it to like the rotary engine seen on cars like the Mazda RX-7 and RX-8 and their predecessors.

This is a great analogy.