Do current US KE penetrators J-hook on impact?

[John Kettler]

Let me explain what I mean. Late in my military aerospace career I got to see some flash radiographs of long rod penetrators hitting armor. They showed a remarkable phenomenon which was wholly at odds with conventional shotline modeling for terminal ballistics of KE projectiles before we adopted Sabot using long rod penetrators. The LR penetrators were observed to first bite into the armor, then driven by the now redirected momentum, go through the plate at considerably less effective thickness than the shotline model would predict. Would say the hooking effect was at something of the order of 70 degrees relative to the armor plate, or practically normal to it. Once through the armor, the proectile would push in, and would continue to curve, resulting in the J in the description. Our early long rod penetrators were rather spindly, but I was wondering whether the shift to thicker, heavier penetrators more resistant to shearing forces and other side attacks have now returned impact phenomenology to something more akin to shotline paths?

J-hooking is described in Penetrators over on Global Security, but I'm having access problems.

https://www.globalsecurity.org/military/systems/munitions/penetrator.htm

Regards,

John Kettler 

[Sgt.Squarehead]

Here's the sum total of that article's commentary on the subject:

This is accomplished while maintaining a stabilized, penetrating trajectory which is a trajectory which does not include "J-hooking" instabilities or diversion of the penetrator off its intended path.

 

[John Kettler]

Andy,

Thanks. Changed search terms and tried a different approach, which is how I found this declassified RARDE report on the penetration of long rod penetrators. the first thing I noticed was that the authorization to publish was by a Principal Superintendent 'D' Division S.W. Coppock, a name which instantly brought me up short, for it is the same last name as the co-inventor of APDS, which came out of RARDE. The report was written in 2006, and I don't know British defense establishment retirement rules, but either we have THE man himself, presuming he wouldn't have been retired and was, say, 20, when he helped bring forth APDS or, more likely, a relation, with my money on a son. A quick skim didn't find J-hooking, but it is quite the tour of long rod penetrator theory and testing going back to the mid 1960s.

http://www.dtic.mil/dtic/tr/fulltext/u2/595793.pdf

Progress! This is math heavy, but the text is more than adequate to follow the argument. What's shown here, using, inter alia, X-Ray photography is that LR penetrators do bend on impact. Am of the opinion the US M829A4 AKA flying battering ram, is specifically designed NOT to flex much, but does this at the expense of lower velocity because of increased mass and drag.

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.537.6050&rep=rep1&type=pdf

Performance optimization of a long rod penetrator penetrating into a semi-infinite target considering bending characteristics

Khodadad VAHEDI1, Hassan ZOHOOR2, Alireza NEZAMABADI3, Mojtaba ZOLFAGHARI3
1Department of Mechanical Engineering, Imam Hossein University, Tehran-IRAN
2Center of excellence in Design, Robotics and Automation,
Sharif University of Technology-IRAN
3Department of Mechanical Engineering, Islamic Azad University-Tehran Sciences and Research Branch-IRAN
e-mail: alireza.nezamabadi@gmail.com
 

The search term I used was "penetration phenomena for long rod ke projectiles" and got a lot of LR material to trawl through.

Regards,

John Kettler