Share this on Facebook
download .zip with all pictures
Well, him actually. He’s absolutely correct. There’s not predefined vapor cone that happens right at the sound barrier, it’s any time there’s large differences in pressure/flow over the surface of the plane. In this case, it seems high AoA reduced pressure on top of the flight surfaces, causing humid air to condense out the water vapor.
You’ll also get the full vapor cone in the transonic region, mach 0.8-1.0 range, due to a mixture of subsonic and supersonic flow regimes on the aircraft.
EDIT: Transonic region correction. Bit of a typo there
EDIT 2: Don’t think I dislike the picture though, it’s awesome! The F-15 is a really kick ass plane (and WAY fast, even among fighters)