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Re: Super

From: Dale Brunson <dbrunson@owt.com>
Hey Gang, here is a special treat!

Every so often, just the right combination of conditions and events
occur to create an unbelievable event, in this case an F-18 passing
through the sound barrier.
Not only were the water vapor, density, and temperature just right,
but there just happened to be a camera in the vicinity to capture the
moment.
The F-18 is actually in transonic flight, with normal shock waves
emanating from behind the canopy and across the wings and fuselage. The
condition will last for only an instant, and once supersonic flow exists
completely around the aircraft, sharp angled sonic cones replace the
normal shock waves.
The odds of getting a shot like this are staggering.

Enjoy - Dale>

(I haven't decoded that photo, and I'm assuming that it's the same as the
one in last week's newspaper.)

I think the above explanation is inaccurate. "Sharp angled sonic cones"
only exist when an aircraft is significantly exceeding the speed of sound.
At slightly above the speed of sound, doesn't the shock wave look just
like the cloud in the photo: like a disk?

Also, I think that the effect in the photo is not momentary. As long as
the aircraft maintains that velocity, the shockwave will maintain that
shape. If the humidity and temperature of the environment are fairly
constant, wouldn't that travelling cloud persist for a long time? I
suspect that the situation is not so rare, and the photographer simply
needed to ride in a supersonic aircraft travelling adjacent to the one in
the photo.

I suspect that many people will see that white cloud as being "the sound
barrier", and believe that the aircraft is "flying through it."


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William J. Beaty SCIENCE HOBBYIST website
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