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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Hornady 4DOF Ballistic Program
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<blockquote data-quote="BryanLitz" data-source="post: 1226658" data-attributes="member: 7848"><p>Some clarification...</p><p></p><p>There are many types of modified point mass (MPM) solvers which approximate or neglect various terms for different applications; some are optimized for small arms, some for high angle artillery fire, etc.</p><p></p><p>It seems that one such MPM model has been referred to as a 4 DOF (this is something I wasn't aware of when I wrote my paper, which will be revised to be consistent with this fact).</p><p></p><p>The 4 DOF MPM system of equations seems to have been developed for high angle artillery fire where the yaw of repose grows too big to ignore in this application; both in the drift it creates, and the induced drag (the yaw of repose gets pretty big when trajectories arc thru large angles). The lack of fit between traditional PM models and radar data compelled the ballisticians to 'modify' the PM equations to account for the yaw of repose, which allowed for better agreement between the radar data and the model for such high angle artillery fire.</p><p></p><p>The problem is that this 4 DOF model only calculates yaw of repose, which is enough to get you spin drift, but couldn't calculate aerodynamic jump or limit cycle yaw. Any solver that calculates these additional things requires more than 4 degrees of freedom to do so.</p><p></p><p>-Bryan</p></blockquote><p></p>
[QUOTE="BryanLitz, post: 1226658, member: 7848"] Some clarification... There are many types of modified point mass (MPM) solvers which approximate or neglect various terms for different applications; some are optimized for small arms, some for high angle artillery fire, etc. It seems that one such MPM model has been referred to as a 4 DOF (this is something I wasn't aware of when I wrote my paper, which will be revised to be consistent with this fact). The 4 DOF MPM system of equations seems to have been developed for high angle artillery fire where the yaw of repose grows too big to ignore in this application; both in the drift it creates, and the induced drag (the yaw of repose gets pretty big when trajectories arc thru large angles). The lack of fit between traditional PM models and radar data compelled the ballisticians to 'modify' the PM equations to account for the yaw of repose, which allowed for better agreement between the radar data and the model for such high angle artillery fire. The problem is that this 4 DOF model only calculates yaw of repose, which is enough to get you spin drift, but couldn't calculate aerodynamic jump or limit cycle yaw. Any solver that calculates these additional things requires more than 4 degrees of freedom to do so. -Bryan [/QUOTE]
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Hornady 4DOF Ballistic Program
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