[RunningWolf]

Those type formations are caused by high velocity exhaust streams out of a nozzle. As the exhaust stream cools off/slows down, it begins to form its own vortices that will curl in in on each other like you see. Due to various dynamics/irregularities in the atmosphere and the exhaust stream vortices themselves, a few will become large enough to make the donut formations that we see down on the ground.

For what it is worth, I do not see the pulse-jet as a viable platform for a M4+ engine. For one thing it would beat itself and the airframe up pretty hard, and both would have a very low service limit. I would have to think that thing would also be very un-stealthy to acoustical detection modes, maybe others too.

But if it was a pulse jet, the exhaust pulses would be much more pronounced and at regular intervals than we have always seen in these photos.

Wolf

[TXnMA]

"But if it was a pulse jet, the exhaust pulses would be much more pronounced and at regular intervals than we have always seen in these photos."

And almost certainly more numerous and closer together (higher pulse-rate frequency)...

[doorgunner69]

For what it is worth, I do not see the pulse-jet as a viable platform for a M4+ engine. For one thing it would beat itself and the airframe up pretty hard, and both would have a very low service limit.

That's my thought also: the vibration from the pulsed detonations would be very destructive.

[VaBthang4]

Thank you for what appears to be the one competent, insightful post of this thread.

The gene pool is getting pretty shallow here @ FR.