Re: Sonic Boom

From:         pilon@aem.umn.edu (Anthony Pilon)
Organization: University of Minnesota, Twin Cities
Date:         14 Oct 93 23:57:15 PDT
References:   1 2
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grichard@midway.uchicago.edu (Rich Benzinger) writes:
>>krzystek@carson.u.washington.edu asks:

>>
>>  P.S. Can somebody please elaborate on the original question:
>>does the sonic boom arise only on passing through the sound barrier,
>>or during the whole supersonic flight?


In short, during the entire supersonic flight.  Acceleration and decelleration
while supersonic can also cause amplification of the boom.

>	By analogy, the smooth surface of the water in front of the speeding
>boat implies that one does not hear a supersonic aircraft approaching.
>Further, the boat's triangular wake is the counterpart to the conic shock
>wave behind an aircraft at mach > 1.  Thus the "boom" occurs as the wave
>passes over the rowboat, plate glass window, eardrum...

>	Of course, I'm willing to be shot down by more learned authorities...

>	Hope this helps.

I'm not exactly sure how learned I am, but this analogy makes sense.  The
only thing it doesn't account for is the shock created at the tail of the
A/C.  In a boat there's a wake.  For a supersonic A/C there is a shock wave.
The two main shocks (nose and tail) are the cause of the "double bang" felt
on the ground.

Hope this helps instead of confuses.

					Tony Pilon
					pilon@aem.umn.edu

>					Rich Benzinger
>					grichard@quads.uchicago.edu

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    "It could be worse....                     Anthony Pilon
       ...it could be rainin'"         Aerospace Engineering, U of MN
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