ASPIRE-ing To Go Supersonic AND Hear OR Detect It...

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AFAIK: Formation of a sonic boom/crack/whatever is the result of an object exceeding the local speed of sound. Size is not an overriding factor.

Read what Tim Van Milligan of Apogee Components has written about Apogee's "Aspire" rocket kit.


I think you may have misunderstood my post. I'm not saying a rocket can't make a sonic boom, I'm saying model rockets create one that is too low a volume to hear over the ambient noise. The Apogee Aspire is so small the over pressure generated would be most definitely lost in the back ground noise.

Here's a quote from Wikipedia on the sonic boom page ..."The power, or volume, of the shock wave depends on the quantity of air that is being accelerated, and thus the size and shape of the aircraft."

https://en.wikipedia.org/wiki/Sonic_boom
 
FWIW, I honestly DO NOT REALLY KNOW whether I will ever make this idea actually work or not.

That said, a couple of days ago I thought of a statement of sorts to address the challenges to getting this done. Although I do not consider myself a southerner, I am a native Floridian. So let me just say...

"HOLD MY BEER...."

:wink:
 
I believe I can add some valuable insight to this discussion. My qualifications are 45 years working in the NVH field. The first 40 years for the world’s largest manufacturer of small engines and the last 5 years for the largest manufacturer of motorcycles in the USA.

First, regarding the kite video it is apparent that a component in the kite is causing an impact noise possibly to the camera case itself. This is the sharp rapping or knocking sound heard. Second, GoPro cameras are notorious for wind noise. With the open back case, wind only a few miles per hour will be very audible.

Professional wind screens are made of special open-cell foam about 4 inches in diameter and are designed to minimize any effects on the frequency spectrum. We routinely used them in our indoor facility to protect the expensive microphones ($700) from damage should the stand inadvertently be knocked over. For the typical wind speeds encountered a few hundred feet above the ground they would do a good job minimizing wind noise.

I found a paper from Montana State University called “Summary of Gun Shot Acoustics” which has a lot of good information about recording the sound of shock waves for rifle bullets. The link is here: https://www.montana.edu/rmaher/publications/maher_aac_0406.pdf
For velocities just over Mach 1 the angle of the shock wave is nearly 90 degrees to the travel of the rocket. This would make it impossible to hear from the ground as has been stated before.

I think the biggest problem will be distinguishing the sound of the sonic boom from the sound of the rocket motor. If the noise level of the motor is 10 dB or more above the sonic boom it will be very hard to separate it out. The noise from the rocket motor is broad-band noise caused by turbulence of the rocket exhaust “tearing” at the (comparatively) still surrounding atmosphere. The sonic boom is a short impulse called a “N” wave due to its shape. Possibly it could be “dug out” of the rocket jet noise with careful analysis.

I think recording a sonic boom from a model rocket is going to be extremely challenging. Kudos to the first person to accomplish this feat.

Tom
 
Great post, Tom.

I think recording a sonic boom from a model rocket is going to be extremely challenging. Kudos to the first person to accomplish this feat.

Indeed so. With the qualifier, of convincingly proving that the sonic boom really is a sonic boom, and not possibly any other noise.

Otherwise, I'm sure there are already old videos/recordings of "recorded sonic booms" from vertically launched hobby rockets, which are noises of something but not necessarily what was claimed (as per the human ear based claims as far back as the 1970's with the FSI "******" rocket system. Where the staging "pop" is likely what was heard some time after it was seen to stage visually).
 
kite's shadow looked like a double French Military/delta design. Right?


K'Tesh, you are correct. That kite's shadow tells me it is a double delta conyne kite. Here are a BUNCH of photos of other conyne-type kites: https://www.google.com/search?q=dou...oAhVOc98KHUEKD8YQsAR6BAgJEAE&biw=1366&bih=633
Delta Conyne kites can also have one single triangular center 'cell', or more than two.

All that SOUND from that Kite Aerial Video makes me think that some part {or parts} of the frame of that kite is {are} loose. OR the camera itself is not mounted very securely to the kite, and is bumping into - or being bumped by - the kite's frame. The kite appears to be flying okay, so whatever is causing it cannot be too catastrophic.

FWIW, I am into kites as well as rockets.

Note: I have NOT been logged into the forum - nor done much rocket stuff - for at least two years. Also, it's is about 03:30 {3:30 AM} EDT local time. Cannot sleep. I mention this so if this post is 'rambling' a bit, at least MORE than usual for me , that is why.
 
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