Re: breaking sound barrier movie

[Stefan Jeglinski <jeglin@4PI.COM>]

>  >    Concerning the photograph mentioned in J. Marsh's post:
>  >could someone explain the accompanying description claiming
>  >that "part of the plane is supersonic and part isn't"?
>
> I have the idea that the air around the aircraft might not
> be entirely at rest. The flow of air past the aircraft at
> its boundary might well vary over the surface. It is also
> possible that the air is not isothermal. The speed of sound
> varies as the square root of the temperature.

This makes sense to me. The base definition of supersonic (Mach > 1,
right?) is simply the speed of the object relative to the local speed
of sound in the medium. Given pressure and temperature variations, I
would not be surprised if by definition one part of the aircraft is
supersonic while another is not, despite every part of the aircraft
traveling at the same speed. I would agree the statement tends to
confuse rather than elucidate.

Can anyone explain why the movie clearly shows *2* "cloud" events?
Early in the frames, there is an obvious formation of vapor which
then dissipates completely before the second. Is such a cone formed
when crossing the barrier back to subsonic? If so, maybe the craft is
only briefly travelling at Mach > 1?


Stefan Jeglinski