The propagation of Kaboom

[Brian Roselle]

Thanks Brian, your description does appear to me to be what I obtained from the Montana State University Summary and another source which was just some comments on another forum. If I understand the particulars of the speed of the Carcano bullet, it is approximately Mach 2. So using the formula in the MSU Summary, I came up with an angle of 30-degrees from the path of the bullet to the cone of the shockwave. Hopefully that is a reasonable approximation of the angle at the initial muzzle velocity anyway.

Yes, That sounds about right to me.

Your post peaked my interest on what I was saying in the past. I'll look and hopefully is was consistent with this 

[Brian Roselle]

Charles, I realized your thread here related to the shock waves you are exploring relates significantly to some z313 shot theories. I don’t want this discussion to get sidetracked, but your shock wave angle calculation of 30 deg directly raises a key issue.

There has been a major point being published by some researchers to help prove a z313 shot came from the Grassy Knoll.
Their supporting evidence is twofold.

A blur in Zapruders film at z313 could not have been caused by a startle reflex reaction, so it was:
1) A supersonic bullet going at least Mach 2 (M=2) and purportedly Mach 3 (M=3) or preferably Mach 4 (M=4), coming from a bullet shot from behind the fence on the grassy knoll and
2) The shock wave caused Zapruder’s camera to be displaced by virtue of it striking and shaking Zapruder and/or his camera right at z313.

Their argument sounds decent on the surface, but one that I think is just a gut-feel, grasping in air hypothesis that was never checked out.
I’m not sure if a bullet shock wave coming from Zapruder’s right would even be enough to nudge his camera (and probably not based on a video I saw below), but perhaps the easiest way to evaluate this scenario is to measure the angle formed from the hypothesized shooter’s position, to JFK, and to Zapruder at frame z313 and then compare that to the proposed frontal bullet Mach angle. If the angle formed by the (shooter/JFK/Zapruder) positions is greater than the Mach angle formed by the bullet at strike at z313, then the shock wave never reached Zapruder in time to cause the blur. If I call the shooters position point S (that is about 12 feet west from the north turn in the grassy knoll fence), and JFK’s position is K, and Zapruder’s position is Z, then the angle formed, / SKZ on the Google Earth map, is 36 deg

The Mach angle mu is calculated as mu=sin^-1(1/M)
For M = 2 then mu=30 deg (as you calculated. It is marked in as a green line here on the diagram)
For M = 3 then mu=19.5 deg
For M = 4 then mu=14.5 deg

All these angles are all smaller than the observed personnel positioning angle of 36 deg, and the higher the Mach value the worse it gets. The shock wave never got to Zapruder in that time.



Secondly, here is an interesting video on how although a shock wave can sound loud when close to you and can obviously move your eardrum, it doesn’t do much else. In the video they had much more trouble with small gusts of wind on a house of cards than with a 50 BMG Mach 3 shock wave.

https://www.wideopenspaces.com/can-the-shockwave-from-a-50-bmg-really-kill-you/

[Jerry Freeman]

Mr. Euins: Well, when he stuck it out, you know--after the President had come on down the street further, you know he kind of stuck it out more, you know.
Mr. Specter: How far was it sticking out of the window would you say then, Amos?
Mr. Euins: I would say it was about something like that.
Mr. Specter: Indicating about 3 feet?
Mr. Euins: You know--the trigger housing and stock and receiver group out the window.
Mr. Specter: I can't understand you, Amos.

Who could?

That’s interesting ...

It sure is. Forget about muzzle blasts and sonic shock waves...That places a sniper hanging out that window by his knees.
What about the gun rest box--you know..the one with the scar on it? Someone probably put it back huh?

[Charles Collins]

Charles, I realized your thread here related to the shock waves you are exploring relates significantly to some z313 shot theories. I don’t want this discussion to get sidetracked, but your shock wave angle calculation of 30 deg directly raises a key issue.

There has been a major point being published by some researchers to help prove a z313 shot came from the Grassy Knoll.
Their supporting evidence is twofold.

A blur in Zapruders film at z313 could not have been caused by a startle reflex reaction, so it was:
1) A supersonic bullet going at least Mach 2 (M=2) and purportedly Mach 3 (M=3) or preferably Mach 4 (M=4), coming from a bullet shot from behind the fence on the grassy knoll and
2) The shock wave caused Zapruder’s camera to be displaced by virtue of it striking and shaking Zapruder and/or his camera right at z313.

Their argument sounds decent on the surface, but one that I think is just a gut-feel, grasping in air hypothesis that was never checked out.
I’m not sure if a bullet shock wave coming from Zapruder’s right would even be enough to nudge his camera (and probably not based on a video I saw below), but perhaps the easiest way to evaluate this scenario is to measure the angle formed from the hypothesized shooter’s position, to JFK, and to Zapruder at frame z313 and then compare that to the proposed frontal bullet Mach angle. If the angle formed by the (shooter/JFK/Zapruder) positions is greater than the Mach angle formed by the bullet at strike at z313, then the shock wave never reached Zapruder in time to cause the blur. If I call the shooters position point S (that is about 12 feet west from the north turn in the grassy knoll fence), and JFK’s position is K, and Zapruder’s position is Z, then the angle formed, / SKZ on the Google Earth map, is 36 deg

The Mach angle mu is calculated as mu=sin^-1(1/M)
For M = 2 then mu=30 deg (as you calculated. It is marked in as a green line here on the diagram)
For M = 3 then mu=19.5 deg
For M = 4 then mu=14.5 deg

All these angles are all smaller than the observed personnel positioning angle of 36 deg, and the higher the Mach value the worse it gets. The shock wave never got to Zapruder in that time.



Secondly, here is an interesting video on how although a shock wave can sound loud when close to you and can obviously move your eardrum, it doesn’t do much else. In the video they had much more trouble with small gusts of wind on a house of cards than with a 50 BMG Mach 3 shock wave.

https://www.wideopenspaces.com/can-the-shockwave-from-a-50-bmg-really-kill-you/

Thanks Brian, the way I understand it is that the shockwave travels at the speed of sound in a direction 90-degrees to the angle of the cone. So say at Mach 2 the bullet is moving twice as fast as the shockwave. Therefore for the shockwave to reach Zapruder before the bullet reaches JFK, the distance from the shooter to JFK would have to be more than twice the distance from the shooter to Zapruder. It is clear from your diagram that this is not the case. And I agree that the faster bullet speeds would only make the difference even greater. The Montana State University study summary explains this and even shows graphs of the recordings which prove it to be true. And I agree the shockwave wouldn’t be powerful enough to physically move the camera. It might startle Zapruder into moving the camera but the reaction time for that to happen has to be considered also. Interesting video, thanks!

[Brian Roselle]

I think I should add a couple of points to help explain this diagram some more.

First, this diagram is all based on a theoretical shot from the knoll striking JFK at z313. In this diagram I think the top end of that green line (which would be where the outside edge of the shock wave cone's base would be) would likely need to be extended upwards a little bit further than shown here. That would have that green line, as it moves in a direction perpendicular to itself, likely cross Zapruder's position but it would be after z313 so it could not be the cause of the Z313 shake. At higher mach values the green line would tilt further to the left, farther away from Zapruder and arrive to him even later.  From the line diagrammed here onward in time, the green line shock wave would continue to move basically up the street parallel to Elm at that location at the speed of sound.

Also there would be a symmetric green line 30 deg below or South of the bullet path line segment SK representing the shock wave at ground level that is the from the other half or side of the total shock wave cone, moving generally downwards towards Main St.

I hope this helps a little more. Let me know if more clarification is needed.

[Charles Collins]

I think I should add a couple of points to help explain this diagram some more.

First, this diagram is all based on a theoretical shot from the knoll striking JFK at z313. In this diagram I think the top end of that green line (which would be where the outside edge of the shock wave cone's base would be) would likely need to be extended upwards a little bit further than shown here. That would have that green line, as it moves in a direction perpendicular to itself, likely cross Zapruder's position but it would be after z313 so it could not be the cause of the Z313 shake. At higher mach values the green line would tilt further to the left, farther away from Zapruder and arrive to him even later.  From the line diagrammed here onward in time, the green line shock wave would continue to move basically up the street parallel to Elm at that location at the speed of sound.

Also there would be a symmetric green line 30 deg below or South of the bullet path line segment SK representing the shock wave at ground level that is the from the other half or side of the total shock wave cone, moving generally downwards towards Main St.

I hope this helps a little more. Let me know if more clarification is needed.

Yes, that’s the way I understood it. I can easily get confused when adding or subtracting the angles involved and usually need to draw a diagram similar to yours in order to arrive at the correct conclusions. Of course these one dimensional diagrams are a simplification of what happens in the actual 3-D world, which includes the elevation changes (especially of the sixth floor window). But these diagrams can give us a rough idea of who was or wasn’t affected by a direct shockwave from the bullets.

[Brian Roselle]

Yes, that’s the way I understood it. I can easily get confused when adding or subtracting the angles involved and usually need to draw a diagram similar to yours in order to arrive at the correct conclusions. Of course these one dimensional diagrams are a simplification of what happens in the actual 3-D world, which includes the elevation changes (especially of the sixth floor window). But these diagrams can give us a rough idea of who was or wasn’t affected by a direct shockwave from the bullets.

Good point Charles. What I described is how I understand and what I would call the standard behavior of the shock wave. Something I forgot to consider here is the ground and changes in elevation that would have a role in what is encountered (like some reflection off the ground), and if there were other structures in its path, those blockages or reflections could also come into play etc. 
But hopefully the basic behavior should help anticipate what will generally transpire.

[Charles Collins]

The principal reason for me to begin this study is to explore a possible reason that many witnesses said the first shot sounded different than the other two shots. Some have suggested that the second two shots had the distinctive sharp crack of a high powered rifle but that the first shot sounded more like a firecracker or backfire. The shockwave created by the supersonic bullet is a big part of why the high powered rifles have the distinctive sharp crack sound. The shockwave is propagated much like a boat wake on the surface of a body of water (but in three dimensions). If a motor boat were to stop or slow down below "wake speed" a significant wake is no longer created. The same thing happens with a supersonic bullet (and it's shockwave) that stops or is slowed below the speed of sound.

I have taken Don Roberdeau's map and drawn some lines representing the various scenarios that I believe might have taken place in Dealey Plaza on 11/22/63. The first such image represents what I believe to be a rough idea of the propagation of the shockwave from a bullet that hits the mast of the traffic light in front of the TSBD.




The yellow outline represents the limits of the area on the ground that I believe would be affected directly by the shockwave of a bullet that hits the mast of the traffic light and is slowed below the speed of sound at that point. I calculate this area to be roughly 25,594 square feet.

The other scenario diagrams that I have prepared will follow as time permits.