Subject: Re: Breaking the Sound Barrier
From: arno@utu.fi (Arno Hahma) 
Date: Feb 22 1996
Newsgroups: rec.models.rockets

In article <1996Feb19.214229.1512@hccompare.com>,
 <kaplowro@hccompare.com> wrote:

>been too long, and I don't remember the formula, but at exactly Mach 1 the
>angle is 180 degrees. As the speed increases, the cone gets more pointed.

arcsin (1/M) gives the half angle. Thus, it is 90 degrees for Mach 1;
multiply by 2 to get 180 degrees for the Mach cone tip angle.  Mach 2
would give a 60 degree Mach angle.

>It will NEVER hit the ground at the point below the rocket, no matter what
>the speed. Thus an observer listening for the boom must either be up in the

No, but you can hear the echo from the surroundings, if you send the
rocket at, say, 30 degrees angle from the horizontal plane.  At least a
57 mm rocket makes really audible, diminishing, ripping noise, when it
flies at about mach 2. It sounds somewhat like a jet plane passing
over at low level.

>       Bob Kaplow                      INTERNET: kaplowro@hccompare.com

ArNO
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