Alan Erskine wrote:

Other than the two mentioned, what can be used for stage sep?


You could sever them using a linear shaped charge around the body of the
vehicle.
This would have a advantage over multiple explosive bolts in that the
whole thing would fire at once from a single detonation point, improving
reliability.
The odd stage separation of flight two makes it look like one explosive
bolt fired late or not at all, causing the engine bell to hit the
interstage structure as the first stage fell away.

Pat