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Rifles, Reloading, Optics, Equipment
Equipment Discussions
Which weather station, Pocket PC, and Balistic Program?
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<blockquote data-quote="Gustavo" data-source="post: 146112" data-attributes="member: 6"><p>[ QUOTE ]</p><p>[ QUOTE ]</p><p> Also does this program account for gryrscopic lateral and vertical movements associated with a right or left twist barrel (Precession, Magnus, Bernoulli's, Coning, Yaw of Repose) or do you have to figure that out on your own? </p><p></p><p>[/ QUOTE ]</p><p></p><p>For any program to account for these effects, the method used must be a numerical 6-DOF, and of course, you must have at hand the ( a considerable number ) the aerodynamics coefficients for YOUR particular bullet.</p><p></p><p></p><p>( Total angle of attack in Radians, Axial force coefficient, Normal force coefficient derivative (1/rad), Overturning moment coefficient derivative (1/rad), Magnus moment coefficient derivative (1/rad), Pitch damping moment coefficient, Spin decay roll moment coefficient )</p><p></p><p></p><p>Be aware this approach has two main issues.</p><p></p><p></p><p>One, you need such a kind of facility ( plus the money and engineers ) to obtain the coefficients that's only available to the goverment's labs unless you can afford it...then, the 6-DOF needs a LOT of computer resources to yield a good solution, which absolutely precludes it to be used on a PDA.</p><p></p><p></p><p>Same problem was faced by the USAF years ago, and they turned to a modified Siacci's solution.</p><p></p><p></p><p>Moreover, I really doubt that you need to account for these gyroscopic and viscous effects except you are going to shoot from a moving vehicle at high speed, while at the same time trying to hit a target a couple of miles away.</p><p></p><p></p><p>However if you insist on having these effects accounted for you can precalculate them ( again with a 6-DOF model ) and then incorporate its values to your trajectory.</p><p></p><p></p><p>In short, for some of the reasons aforementioned, today, even the military for some cases, uses analytical closed-form solutions. Of course, discussing which is best is another question! since I have my own preferences. /ubbthreads/images/graemlins/grin.gif</p></blockquote><p></p>
[QUOTE="Gustavo, post: 146112, member: 6"] [ QUOTE ] [ QUOTE ] Also does this program account for gryrscopic lateral and vertical movements associated with a right or left twist barrel (Precession, Magnus, Bernoulli's, Coning, Yaw of Repose) or do you have to figure that out on your own? [/ QUOTE ] For any program to account for these effects, the method used must be a numerical 6-DOF, and of course, you must have at hand the ( a considerable number ) the aerodynamics coefficients for YOUR particular bullet. ( Total angle of attack in Radians, Axial force coefficient, Normal force coefficient derivative (1/rad), Overturning moment coefficient derivative (1/rad), Magnus moment coefficient derivative (1/rad), Pitch damping moment coefficient, Spin decay roll moment coefficient ) Be aware this approach has two main issues. One, you need such a kind of facility ( plus the money and engineers ) to obtain the coefficients that's only available to the goverment's labs unless you can afford it...then, the 6-DOF needs a LOT of computer resources to yield a good solution, which absolutely precludes it to be used on a PDA. Same problem was faced by the USAF years ago, and they turned to a modified Siacci's solution. Moreover, I really doubt that you need to account for these gyroscopic and viscous effects except you are going to shoot from a moving vehicle at high speed, while at the same time trying to hit a target a couple of miles away. However if you insist on having these effects accounted for you can precalculate them ( again with a 6-DOF model ) and then incorporate its values to your trajectory. In short, for some of the reasons aforementioned, today, even the military for some cases, uses analytical closed-form solutions. Of course, discussing which is best is another question! since I have my own preferences. [img]/ubbthreads/images/graemlins/grin.gif[/img] [/QUOTE]
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Rifles, Reloading, Optics, Equipment
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Which weather station, Pocket PC, and Balistic Program?
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