Thank you. I would have missed that, and would not have learned about the condenstaion collar (photo 21).
I would pay more than a quarter for a chance to play #6.
Yep the collar very
briefly occurs when an object transitions to supersonic. There's a popular picture of an F16 (I think) with that collar about midway down the body that's all over the internet. One of those "perfect moment" pictures.
I think. You're basically shaking the water out of the air with the shockwave.