I need work with my math. I count four missiles in the Spike family.
Back in the early 1950’s my Dad was working on a prototype Sidewinder missile. One night he took me to the shop building, a large sheet metal room lined with workbenches, tools and what I later learned, were oscilloscopes.
In the middle, sitting on pipe stands, was a missile about ten feet long with a huge fish-eye lens on the nose. Dad took me around to the back end and told me to watch the fins. Then he walked in front of the fish eye lens and waved his cigarette around.
The fins followed his cigarette! Amazing! (I think I was about 7 years old at the time)