[roc-chat] Re: Interested in Sonic Boom Sound

It still was unusual compared to the many rockets that reach that speed and do not pop.   Perhaps it was a perfect storm of  shape, size, speed, altitude, and weather.  So, do we know if it actually did reach the speed of sound?

-----Original Message-----
From: Lakestake Rocketry
Sent: Jun 14, 2012 6:18 PM
To: roc-chat@xxxxxxxxxxxxx
Subject: [roc-chat] Re: Interested in Sonic Boom Sound

Kurt, Google "speed of sound".  ;)

A pop heard half a second after burnout at an average temperature of 25 degrees C travels at approximately 346m/sec.

If the event occurred at a altitude of 340 meters the pop would have happened 1/2 second before burnout and been heard half a second after (give or take the spedd of light).  If burnout was higher it happened even earlier.

Matt

On Jun 14, 2012 6:08 PM, "Kurt Gugisberg" <kurtgug@xxxxxxxxxxxxx> wrote:
Richard, I heard it too.  Seemed to me it was shortly after burnout which makes it even more mysterious.  I was watching the flight and, as far as I can visualize it,  the burn ended and and half second or more later, the pop.

Kurt
-----Original Message-----
From: Richard Dierking
Sent: Jun 14, 2012 8:49 AM
To: roc-chat@xxxxxxxxxxxxx
Subject: [roc-chat] Re: Interested in Sonic Boom Sound

Ok, glad that someone else heard this Mike!  And yes, this sounds like a very good explanation.  I was a sharp pop and that's what surprised me.  Do you know who's rocket it was?  Just wondering if there's video out there.
 
Thank you,
Richard

On Thu, Jun 14, 2012 at 12:29 AM, Mike Riss <rockt_dude@xxxxxxxxxxxxx> wrote:
Richard,

I think I heard the same thing, and IIRC, I was standing in the safety zone at the time.  Seemed like it was towards the end of the motor burn.  It sounded pretty sharp to me.  I was thinking it was that "liner getting expelled" that usually gets thrown out as an explanation for that type of sound.

Mike

--- On Wed, 6/13/12, Richard Dierking <richard.dierking@xxxxxxxxx> wrote:

From: Richard Dierking <richard.dierking@xxxxxxxxx>
Subject: [roc-chat] Interested in Sonic Boom Sound
To: roc-chat@xxxxxxxxxxxxx
Date: Wednesday, June 13, 2012, 8:20 AM

During ROCstock after I was doing some maintenance on one of the back pads and was walking away, a rocket was launched.  It was about a 4" diameter, and had a large enough motor to get it going fast.  During the flight, I definitely heard a "pop" but it didn't coincide with any event I saw on the rocket.  I thought that a sonic boom could only be heard if the cone created by the disturbance passed by you.  So, what could this have been?  I was thinking perhaps a sound generated by turbulence at the base of the rocket?
 
Anyway, this is the first time I've heard this kind of sound and I wonder if someone has video that includes this "pop."
 
Richard Dierking

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