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From: rjnoe@riccb.UUCP (Roger J. Noe)
Newsgroups: net.space,net.columbia,net.aviation
Subject: Re: Shuttle sonic booms
Message-ID: <600@riccb.UUCP>
Date: Wed, 4-Dec-85 17:54:08 EST
Article-I.D.: riccb.600
Posted: Wed Dec  4 17:54:08 1985
Date-Received: Fri, 6-Dec-85 06:30:13 EST
References: <8512040306.AA22588@s1-b.arpa>
Organization: Rockwell International - Downers Grove, IL
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Xref: watmath net.space:4876 net.columbia:1726 net.aviation:2237

> Why are there two sonic booms from the shuttle?

It's because there are two "sonic cones" formed by the shuttle.  (There is
very likely a more scientific term for this, but I don't know what it is.)
With most supersonic aircraft, a cone-shaped shock wave expands from the
nose of the craft outward.  Where and when this cone intersects the surface
of the Earth determines who hears the sonic boom.  This cone usually expands
at a wide enough angle to engulf the rest of the aircraft.  But the shuttle
has a pretty unusual shape.  I think the vertical stabilizer (tail) rises
above the cone-shaped shock wave formed by the nose.  This causes the tail
to slam into the surrounding air the same way the nose does, and a second
shock wave, also shaped like a cone, forms at the edge of the tail.  This
is the explanation I have heard, anyway.  I don't think the two sonic booms
are from the top and bottom points of the "N-signature" of the shock wave
formed at the nose, or else every supersonic aircraft would exhibit this
phenomenon.  I used to hear F-4's go over my house many years ago, and I never
remember hearing a double sonic boom, although sometimes two or more Phantoms
would be in formation and each would have its own sonic boom.  Could someone
elaborate on this, please?  At least let me know if this is all accurate.
Thanks.
--
	Roger Noe			ihnp4!riccb!rjnoe