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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Ballistic Program Inconsistencies
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<blockquote data-quote="jeffjackson" data-source="post: 312367" data-attributes="member: 14728"><p>Bryan,</p><p> </p><p>Good point on the velocity vs. mach for temp. I had thought about that at one point but didn't do any experiements to measure the affect/outcome, etc. You've piqued my interest again though <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" />. The other place I noticed was that when people convert from sea level pressure to station pressure I think some use the station temperature in the conversion and some don't. I arrived at this conclusion more empirically than by examining implementations since I can't look at source for most of the packages out there. I kind of struggled with finding a "good" formula for converting sea level pressure to station pressure.</p><p> </p><p>I thought the Pejsa solution is novel and i think he deserved a lot of credit for coming up with a solution to a problem he was trying to solve at the time; i.e. a set of formulas for a system with limited compute/storage capabilities. I think a lot of folks over the years who approached external ballistics and realized how non-trival it is (solving interdependent differential equations) had the same thought/wish; i.e. surely there is something simplier. Implementation wise I found it very similiar to Siacci. The formulas are definately a lot simplier though. Trying to find the right values for your bullet seems to be problematic. I thought it would be interesting to measure the error of a default set of values that match different standard drag curves to put a number to how closely his formulas and 4 zone approach could get to representing the standard drag curves, but never got back to it. I always thought that might be the limiting factor to his approach but didn't spend enough time with it to say one way or another or if more zones would improve it.</p><p> </p><p>As a computer scientist i found it interesting to contrast and compare the different methods on their compute, space, etc. requirements. While methods like Pejsa and Siacchi are less compute intensize on the trajectory calc. In order to find out things like PBR etc. its additional expense since you end up having to refine your way to solutions to find things that are almost free in the other methods, since you can capture them along the way.</p><p> </p><p>Yes I do have some of my own software. Let me put up a new version and then I'll send you a link. Would love to have any feedback. I have come close to releasing it several times, but always seem to come up with one more thing to do or the day job just takes too much time or consumes too much of my thoughts <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /></p><p> </p><p>Jeff</p></blockquote><p></p>
[QUOTE="jeffjackson, post: 312367, member: 14728"] Bryan, Good point on the velocity vs. mach for temp. I had thought about that at one point but didn't do any experiements to measure the affect/outcome, etc. You've piqued my interest again though :-). The other place I noticed was that when people convert from sea level pressure to station pressure I think some use the station temperature in the conversion and some don't. I arrived at this conclusion more empirically than by examining implementations since I can't look at source for most of the packages out there. I kind of struggled with finding a "good" formula for converting sea level pressure to station pressure. I thought the Pejsa solution is novel and i think he deserved a lot of credit for coming up with a solution to a problem he was trying to solve at the time; i.e. a set of formulas for a system with limited compute/storage capabilities. I think a lot of folks over the years who approached external ballistics and realized how non-trival it is (solving interdependent differential equations) had the same thought/wish; i.e. surely there is something simplier. Implementation wise I found it very similiar to Siacci. The formulas are definately a lot simplier though. Trying to find the right values for your bullet seems to be problematic. I thought it would be interesting to measure the error of a default set of values that match different standard drag curves to put a number to how closely his formulas and 4 zone approach could get to representing the standard drag curves, but never got back to it. I always thought that might be the limiting factor to his approach but didn't spend enough time with it to say one way or another or if more zones would improve it. As a computer scientist i found it interesting to contrast and compare the different methods on their compute, space, etc. requirements. While methods like Pejsa and Siacchi are less compute intensize on the trajectory calc. In order to find out things like PBR etc. its additional expense since you end up having to refine your way to solutions to find things that are almost free in the other methods, since you can capture them along the way. Yes I do have some of my own software. Let me put up a new version and then I'll send you a link. Would love to have any feedback. I have come close to releasing it several times, but always seem to come up with one more thing to do or the day job just takes too much time or consumes too much of my thoughts :) Jeff [/QUOTE]
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