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From: kwan@smeagol.UUCP (Richard Kwan)
Newsgroups: net.columbia
Subject: Re: Columbia down - one sonic boom
Message-ID: <563@smeagol.UUCP>
Date: Fri, 24-Jan-86 20:34:36 EST
Article-I.D.: smeagol.563
Posted: Fri Jan 24 20:34:36 1986
Date-Received: Sun, 26-Jan-86 05:38:10 EST
References: <2884@randvax.UUCP> <639@ttidcb.UUCP>
Distribution: net
Organization: Spacecraft Data Systems, JPL, Pasadena, CA
Lines: 33

In article <2884@randvax.UUCP> jim@randvax.UUCP (Jim Gillogly) writes:
>Columbia landed at Edwards this morning just before 6 AM, PST.  In Topanga
>(Santa Monica mtns above Malibu, CA) we only heard one sonic boom.
In article <639@ttidcb.UUCP>, Jeff Cushner writes:
> Sorry to disappoint you Jim, but I live in Simi Valley, closer by 15 miles
> than you and I heard, very distinctly the normal two booms.

I am not an aero/hydrodyamicist, so I can't speak with authority...

If you look at a ship plowing through a body of water, the bow wave
tends to be very distinct where it meets the bow.  But it seems that
the farther away you get, the more the body of the wave gets spread
out across the surface of the water.  (I think this is likewise for
the stern of the ship.)  After getting very far away from the ship
you would expect the bow and stern waves to each become rather flattened
and start to intersect.  Going out a little further, you should only
perceive one wave.

Now, I'm guessing, because I haven't seen a ship on a sufficiently
still body of water to see the intersection.  In any case, you should
be able to take whatever the two-dimensional hydrodynamic analogy is,
and apply it to the aerodynamics of a shuttle landing with reasonable
safety.

Oh, yes.  I live in the San Fernando Valley.  I remember hearing two
booms.

	Rick Kwan
	JPL

P.S.  Our system has only been on the net for a few months, so I can
imagine someone may have already presented the above arguments.  In
that case, ignore me.