Factors In Terminal Ballistics

[TTK Ciar]

I have been trying to improve my formula for predicting penetration power of small (5mm - 35mm) penetrators at ballistic- and low-hypervelocity-domain velocities, by fitting curves to empirical data and trying to work up valid terms for various penetrator materials and shapes. This has of course opened a huge can of worms.

 

Segmenting the data by all factors (nose shape, penetrator mass, diameter, material type, velocity, mass, and angle of impact) results in too few data points in any given segment to make curve-fitting practical, which always lead me in the past to simplify and choose a narrow domain of penetrator types for which the formula might be valid.

 

Pushing that envelope involves collecting more empirical data, which has resulted in an increase of penetrator types represented in the data, with a variety particularly of nose shapes (ogival, semi-ogival, conical, truncated-conical).

 

Sorting out this mess would be a lot easier if there were a model already worked out for the effect of nose shape on penetration. I don't suppose anyone knows of such a thing? I have looked through my own sources, and have found various treatises on penetration of ogival penetrators through various materials, but none that focus on differences of nose shape penetrating the same target at the same speed, or how different nose shapes influence penetration from different angles, or how different nose shapes influence penetration at different velocities.

 

Before I try to come up with my own (a dubious endeavor; I doubt I have sufficient data), does anyone know of such a beastie?

[Mike Steele]

Maybe ballistic coefficients? Their quite common in handloading....

[Mobius]

My opinion is trying to come up with a universal engineering formula including all nose designs and materials is a fool's errand. Even if you had a testing lab and unlimited time and funding.

[Guest Jason L]

One of the Springer books on ballistics (the author escapes me now and I'm still half a world away from my library) has a significant theoretical treatment of nose shape effects.

 

The math is not pretty and IMO not applicable to the development of any engineering equations.

 

And even then that's somewhat avoiding the issue of penetrator deformation.

 

I think the equations for ballistic penetration even for geometrically simple (spheres L/D =1 rods, etc) shapes are poorly developed. Never mind trying for something comprehensive that also includes nose shape effects.

Edited April 20, 2012 by Jason L

[Art40]

AFAIR, optimal shape for the nose was analytically optimized (with a lot of simplification of course, particularly long rod projectile, perpendicular impact, semi-infinite RHA target etc.) and is conical, with angle about 30 degrees, with truncated end. Optimization of geometry for ogival nose leads mathematically to almost the same shape.

For small caliber, hard core projectiles, conical angle is higher and front is not truncated (with higher angle, top is stronger).

These modification are intended probably to decrease total length of projectile with fixed mass.

 

Forget about engineering equation for all types of geometry and material - you can do it only for particular cases.

Can you imagine engineering formula for optimal nose shape with non perpendicular impact and layered composite target?