@PawelK @GluedToTheScreen Depth charge or Dropped munition set to detonate at the optimal altitude? If it's the latter I'd think fission only with low yield, the gun type. It could be the sphere with potential fusion but I wouldn't expect such a crude system when tolerances are so low for proper initiation. I'll have to look at it again. Something tells me that it is around the altitude that one went off in Japan.

It could have been a counter at Mikoyan for how many planes they downed before the MiG-25 scared the US and the F-15 was created.