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From: scw@ucla-cs.UUCP
Newsgroups: net.space,net.columbia,net.aviation
Subject: Re: Shuttle sonic booms
Message-ID: <8173@ucla-cs.ARPA>
Date: Tue, 24-Dec-85 12:56:30 EST
Article-I.D.: ucla-cs.8173
Posted: Tue Dec 24 12:56:30 1985
Date-Received: Thu, 26-Dec-85 04:01:53 EST
References: <8512040306.AA22588@s1-b.arpa> <600@riccb.UUCP> <386@ubvax.UUCP>
Reply-To: scw@ucla-cs.UUCP (Stephen C. Woods)
Organization: UCLA Computer Science Department
Lines: 35
Xref: watmath net.space:5033 net.columbia:1751 net.aviation:2294

In article <386@ubvax.UUCP> skip@ubvax.UUCP (Skip Addison) writes:
>In article <600@riccb.UUCP> rjnoe@riccb.UUCP (Roger J. Noe) writes:
>>> Why are there two sonic booms from the shuttle?
>>
>>It's because there are [...] anyway.  I don't think the two sonic booms
>> ...
>>--
>>	Roger Noe			ihnp4!riccb!rjnoe
>
>Sonic booms are created by major displacements of air or air rushing in to
>fill a void.  A sonic boom is[...] and sudden abscense of the tail.  A more
>streamlined aircraft has less of a boom.
>
>Notice the two wakes left by some boats at high speeds.  Same principles.

Excuse me, right idea but wrong cause, The shock wave is formed when the air-
flow velocity passes through the speed of sound. If you look at the upper
surface of the wing of any aircraft flying near Mach 1 (Mach .6~~ < v <Mach 1.0)
You'll see 2 'lines' running spanwise, these are 'shock waves' where the airflow
over the wing transistions the speed of sound (increasing veloicity produces
a stronger wave than decreasing veloicity so the forward 'line' will be much
sharper and clearer that the trailing one. The 'lines' will appear to move
forward and backwards on the wing as the airspeed and angle of attack change.
They also move farther apart with increasing Mach number. At Mach 1 the will
be at the leading and trailing edges. If the leading and trailing edges are far
enough apart you'll hear 2 sonic 'booms' as the aircraft passes. Note that the
primary sound energy is produced by the wings (or in the case of the space
shuttle the whole aircraft (being all wing). Now the distance from the nose
to the tail of the space shuttle is what? (150 feet??) so assuming
(20000 feet & Standard Atm. and getting out my trusty pro-star.
Mach 1 = 621 KTAS = 1048 FPS= ~.14 sec between the first boom and the
second, but at 50000 Feet & SA Mach 5= 2743 KTAS = 4629 FPS = .03 seconds
so it sounds like 1 (longer) boom).

<scw>