Transonic Drag

Transonic Drag

Joined: February 17th, 2010, 3:30 am

August 20th, 2012, 4:13 pm #1

I found an interesting graph on Transonic Drag that I thought was worth sharing with you....

[/img]

Note that the drag starts to rapidly increase between Mach 0.80-0.85 (900-950 fps) and has doubled by Mach 0.9 (1000 fps) and tripled by Mach 0.95 (1050 fps).... This means that the extra energy it takes to get a pellet above 950 fps will quickly be shed in the first few yards anyway.... That ties in exactly with the work I have been doing on how the Ballistics Coefficient changes as you push the velocity close to the speed of sound....

Since 950 fps gives you an energy of 2 FPE per grain of pellet weight (an easy number to remember).... this is just one more reason not to push the velocity past that....

Bob
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Joined: April 28th, 2010, 12:23 am

August 20th, 2012, 4:19 pm #2

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Joined: July 4th, 2012, 7:51 pm

August 20th, 2012, 4:46 pm #3

I found an interesting graph on Transonic Drag that I thought was worth sharing with you....

[/img]

Note that the drag starts to rapidly increase between Mach 0.80-0.85 (900-950 fps) and has doubled by Mach 0.9 (1000 fps) and tripled by Mach 0.95 (1050 fps).... This means that the extra energy it takes to get a pellet above 950 fps will quickly be shed in the first few yards anyway.... That ties in exactly with the work I have been doing on how the Ballistics Coefficient changes as you push the velocity close to the speed of sound....

Since 950 fps gives you an energy of 2 FPE per grain of pellet weight (an easy number to remember).... this is just one more reason not to push the velocity past that....

Bob
..changed that much. Ballistic energy is also fighting velocity squared which furthers your point.

Is that graph for a particular ballistic shape, size, smoothness, etc...?

Thanks,


Wyo
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Joined: February 9th, 2006, 10:35 pm

August 20th, 2012, 4:49 pm #4

If you push an airliner beyond 900fps instead of landing in Chicago you land in Cleveland. Just hope it doesn't keyhole.




I plink, therefore I am.
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Joined: April 28th, 2010, 12:23 am

August 20th, 2012, 5:38 pm #5

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Joined: March 1st, 2002, 12:22 am

August 20th, 2012, 6:52 pm #6

I found an interesting graph on Transonic Drag that I thought was worth sharing with you....

[/img]

Note that the drag starts to rapidly increase between Mach 0.80-0.85 (900-950 fps) and has doubled by Mach 0.9 (1000 fps) and tripled by Mach 0.95 (1050 fps).... This means that the extra energy it takes to get a pellet above 950 fps will quickly be shed in the first few yards anyway.... That ties in exactly with the work I have been doing on how the Ballistics Coefficient changes as you push the velocity close to the speed of sound....

Since 950 fps gives you an energy of 2 FPE per grain of pellet weight (an easy number to remember).... this is just one more reason not to push the velocity past that....

Bob
at 35 yards. And I think the gun has more potential than this shooter can extract. Need to get a better trigger guy to wring it out.....

 


dr_subsonic's pneumatic research lab

the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic
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Joined: October 11th, 2011, 6:25 am

August 20th, 2012, 10:04 pm #7

I found an interesting graph on Transonic Drag that I thought was worth sharing with you....

[/img]

Note that the drag starts to rapidly increase between Mach 0.80-0.85 (900-950 fps) and has doubled by Mach 0.9 (1000 fps) and tripled by Mach 0.95 (1050 fps).... This means that the extra energy it takes to get a pellet above 950 fps will quickly be shed in the first few yards anyway.... That ties in exactly with the work I have been doing on how the Ballistics Coefficient changes as you push the velocity close to the speed of sound....

Since 950 fps gives you an energy of 2 FPE per grain of pellet weight (an easy number to remember).... this is just one more reason not to push the velocity past that....

Bob
if you were to push a pellet to 1.5 mach, it could be just as stable as if it were subsonic. not that there is a use in doing this for airguns. kind of defeats the purpose of them. just making sure i understand.
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Joined: March 1st, 2002, 12:22 am

August 20th, 2012, 10:51 pm #8

but that pesky transsonic region will have screwed yer shot before it settles down in the higher mach numbers

dr_subsonic's pneumatic research lab

the Lunatic Fringe of American Airgunning
Southwest Montana's headquarters for Airgunning Supremacy
Proud Sponsor of team_subsonic
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Joined: June 7th, 2010, 12:14 am

August 21st, 2012, 12:06 am #9

Millions of rounds of .22 RF have spent their entire life within the confines of this same "don't go here" trans sonic envelope.

To the enjoyment of thousands and thousands of satisfied gunners

Different strokes for different folk" or Much ado about nothing?
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Joined: July 4th, 2012, 7:51 pm

August 21st, 2012, 1:49 am #10


...and I'm not sure until Bob answers my question above, is that FUBAR zone in the above chart is what you have with a ballistic round designed for subsonic velocity (i.e. pellet skirt). I'm almost positive that PB ballistic projectiles designed for Mach 1 and beyond will not correlate to the Cd graph above. Cd is normally regarded as as constant vis-a-vis velocity. The projectile signature size, density of fluid, and velocity^2 are multiplied to the Cd to determine the energy grabbing drag in LBs Force.

 Or, "everything I just said was B#!!$#!!" lol

 


Wyo
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