Re: but does the pilot hear the sonic boom?

["John S. Denker" <jsd@AV8N.COM>]

On 12/01/2003 04:31 PM, Frohne, Vickie wrote:
> The shock wave travels at *precisely* the speed of sound.

-- This _particular_ type of shock (the sonic boom
in the far field, as heard by an observer on the
ground) is traveling at the speed of sound, because
it is a *weak* shock.

But don't try to generalize this to all shocks.

-- A *strong* shock travels faster than the speed
of sound.  An example is the shock in the air in a
gun barrel ahead of a supersonic bullet.  Another
example is the near field, right near a supersonic
aircraft.  In particular the little piece of shock
right in front of a supersonic aircraft is obviously
supersonic.

http://www.google.com/search?q=weak-shock+strong-shock+oblique

> Does the duck ever intercept its own wake and experience a "water
> boom"? Not likely.

More likely than you might think.  All the duck has
to do is make a sweeping ~180 degree turn and cruise
back through the shock.

==========================================

Also:  To answer a slightly different question:
Even in steady nonturning flight, an observer
aboard the airplane can sometimes *see* the shock.

You can even see a shock near the wing of an
ordinary airliner if you know what to look for,
under favorable conditions.  The air over the
wing is *locally* supersonic when the airliner
is in high-speed cruise, even though the
True Airspeed (as measured, as it should be,
in the undisturbed airstream far from the airplane)
is subsonic....  Choose a seat near the wing root.
The shock looks like a slightly refractive spike
in the air, rather like looking into water or a
piece of glass that has a sharply localized ripple
in it.