Project BRF - Indian APFSDS Ammunition Scenario

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negi
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by negi »

Matrimc wiki most probably takes that info from Fofanov's site however technically speaking the reason why I said I doubt fins riding the bore is very simple , when the round is put into the breech the fins are not exposed they are sorrounded by a tamper which means they are already sub-calibre (they have to be else how will the round fit in) ;when the firing pin goes off and the charge explodes only the penetrator and sabot assembly are propelled in the muzzle , for the fins to ride the bore in true sense they have to be just big enough in diameter as the bore size but if that were the case how come their tips are not visible when round is in it's stock form which means they are sub-calibre in real sense , however they could be bigger than their counterparts from the west as apparent from the images unless we have some dimensions listed we cannot say if they actually ride the bore.

I am yet to get my head around the GRAU indices but following is a decent cutaway of Ru BM-44 round. Look at the fins and their periphery as compared to the diameter of the frontal disc of the sabot it is smaller.

http://fofanov.armor.kiev.ua/Tanks/IMAGES/3bm42001.html
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by Vayutuvan »

Negi, you might be interested in this paper - looks like it is a LS-DYNA hydrodynamic simulation and experimental validation of two types of designs. The graphic (LS-DYNA mesh) show a ring type sabot and 120 mm munition.

[PDF] Jump Error & Gun Dynamics: A Comparison Between Two Types of 120mm Smooth-Bore Tank Guns

Searching on Google Scholar gives me a bunch of papers including two old papers (1988 and 89 resly.) from BRL.

Here is the TR number for "Launch Dynamics of Fin stabilized projectiles" TECHNICAL REPORT BRL-TR-3047

The Effect of Sabot Front Borerider Stiffness on the Launch Dynamics of Fin-Stabilized Kinetic Energy Ammunition

Another search from here - lots of papers (but behind pay wall of AIAA) strike that - they give out only abstracts (for free) but looks they have discontinued sales of the full reports :(

http://www.stormingmedia.us/keywords/sa ... tiles.html

OT but FYI
BRL has an open source CAD software called BRL-CAD (it uses different solid modelling techniques than those in commercial modeling tools like Solid Works for example). That said, they are secondary to the Analysis engines - statics (ANSYS, NASTRAN) and dynamics (LS-DYNA is the preeminent code but is explicit which have advantages disadvantages vis-a-vis implicit codes).
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by rohitvats »

matrimc wrote:<SNIP>Rohit, would that be background enough to start reading n understanding this thread?<SNIP>
matrimc - I must admit upfront that I myself lack any in-depth understanding of the subject. And the main reason for the same is that the subject is highly technical in nature and I lack the requisite background to understand beyond some basic stuff. Someone like you and other BRFites with background in engineering or masters/doctorate in science can better understand the technical matter. And use this knowledge to compare Indian effort in the field with foreign products.

I started the research with the objective to understand the production+supply scenario of this ammunition type. The article dwells into that aspect of the ammunition.

Along the way, I did do some research to understand the subject from technical perspective and pulled some articles as well diagrams - I will put up a technical primer based on this research.

Coming to online research - please search using the word Long Rod Penetrator - that is the American term for APFSDS. There is tonnes of Patent material available online which deals with the subject as well as technical papers.

Some other search strings relevant to topic -

1. Monoblock long rod penetrator - American ammunition is made of single block of Heavy Tungsten or DU with ballistic cap at front.

2. Jacketed long rod penetrator - Technique being tried to address issues with increasing the length of penetrator while keeping the diameter low (L/D Ratio). Rods tend to break or lack requisite terminal ballistics if the length is too long. American I think achieved 30:1 and 40:1 ratios. They are trying covering the rods with some material to increase the performance at high L/D Ratios.
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by rohitvats »

Some images to understand the nuances of APFSDS - All the material has been taken from the internet.

1. Image of Sabot separating from the penetrator after leaving the gun.

Image

2. Russian 3BM-42 APFSDS 'Mango' (we've imported this recently from Russia - Indian designation: AMK-339) - the pictures shows the various components of the round. The tungsten penetrator is encased in a steel jacket which is actually in touch with Ring shaped Aluminium Sabot.

Image

3. American M829A2-T long rod penetrator - The penetrator consists of a single block of Depleted Uranium (DU) with ballistic cap screwed upfront.

Image

4. Another cross section of the American Shot (I think this is with Tungsten Heavy Alloy and not DU) which shows the ballistic cap upfront and mono-block penetrator. The grooves through which Sabot is attached to the penetrator are also seen.

Image

5. Indian Mk-2 125mm APFSDS round clearly showing spindle shaped sabot.

Image

6. Image showing the progression of main Long Rod round for Abrams tanks - one can make out the increasing length of the penetrator and arrangement of penetrator with ballistic cap upfront.

Image

7. Components of training APFSDS round - clearly shows the grooves which attach Sabot with the penetrator.

Image

8. Various designs of components of mono-block long rod penetrator. The top image in the pic below shows mono-block penetrator with grooves for Sabot in the mid-section and grooves for attaching the tail fin assembly+tracer element at the rear.

Image

9. Tungsten Long Rod Penetrator (Pakistan)- you can see the actual tungsten heavy alloy penetrator without the ballistic cap upfront.

Image
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by Vayutuvan »

Rohit, thanks. I read your response. I have some thoughts which I will put down in another thread as they are not relevant here.
The series of photos give a nice visual of the components. With a few actual rounds in hand (more than one as destructive testing may be required to find material properties), one should be able to reverse engineer and modify/enhance according to own needs.
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by Vayutuvan »

Negi, the second photo Rohit posted of 3BM-42 indicates the fins are bore riding. Are you thinking IA redesigned the Russian shots where they replaced the ring sabot with spindle sabot and reduced the fins to sub-bore?
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by negi »

Ok got the real pics for 3BM-42 round

http://www.bocn.co.uk/vbforum/threads/7 ... T-HE/page3

Image

Note that round has 5 fins and Sabot actually is made of 3 pieces. Yes the fins clearly look big enough to ride the bore.
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by rohitvats »

matrimc wrote:<SNIP>In particular what is Orbat? I know what the acronym expands to but what does it mean? What are all the issues and why would one want to carry out this exercise?<SNIP>

Sorry, I did not reply to this part of your question.

Order of Battle (ORBAT) and Table of Organization & Equipment (TO&E) are two methods used to assess the military potential of a nation. Actually, TO&E is a more wider term used to capture Orbat as well as equipment profile of a force.

Example of Orbat: http://orbat.com/site/history/historica ... ert71.html

This helps one to understand the quantum of force in a given context.

Example of TO&E:http://orbat.com/site/cimh/index.html

This helps to understand the firepower and overall potential of the said force.

Both these tables can be prepared at various levels - at national, regional command, Corps, Division, Brigade so on and so forth.

Hope this helps.
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by rohitvats »

matrimc wrote:Negi, the second photo Rohit posted of 3BM-42 indicates the fins are bore riding. Are you thinking IA redesigned the Russian shots where they replaced the ring sabot with spindle sabot and reduced the fins to sub-bore?
Excellent - I see the relevant questions starting to come out.

Here is a cross section image of 3BM-42 round.

Image

Some observations:

1. The fins are sub-caliber to the skin of cartridge - which means they are not of the same caliber as the Sabot.
2. The white band visible around the sabot (called the Obturator band) actually touches the barrel and helps to capture the expanding gases.
3. There is a dip between cartridge case and Obturator band diameter in the shape of a concave shaped structure - this is because once the cartridge case burns off, only the Obturator band is left touching the barrel.
4. The fins have small bulbous shaped structures - visible intact in image above and as sheared off in the image linked by Negi.

Long story short - IMO, fins don't ride the bore literally but touch the barrel through these bulbous structures - keeps the point of contact to minimum (helps reduce the friction) and keep the structural integrity of the fins for further flight.
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by rohitvats »

A great article which explains the development history of Kinetic Energy penetrator.

http://ciar.org/ttk/mbt/papers/symp_19/TB191191.pdf
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by ramana »

Rohit,
The fundamental equations for rod penetrars were developed by Issac Newton. Basically he found two things which are universal even now:
- The depth of penetration is proportional to the ratio of density of the materials interacting. A dense penetrator will penetrate more in a less denser material. Tungsten is the densest material other than DU which one of these days will be taken out.
- All things equal the depth of penetration is proportional to the L/D ratio. A long rod penetrator will penetrate more than the a shorter one. It boils down to kinetic energy per frontal area.

Later it was found that for stability it cannot be a straight rod but have a flare at the end to move the center of stability aft of the center of gravity. Something like feathers on an arrow.

Tungsten rounds were introduced by Germans. And they were pioneers in powder metallurgy. Tungsten also has another property. It doesn't shatter when it endures shock but melts a little/goes plastic and goes on.
DU is a US innovation with all that surplus material. It not only penetrates but it gets oxidised and leaves gases. Jury is out whether to consider it as a chem weapon and leaves heavy metal contamination.
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by negi »

Well from my reading it looks like Sabot has two major roles to play first and the primary one is to act as a plunger of sorts which does not let the gases from charge escape and hence acts as a surface against which gases push against and propel the entire Sabot+Penetrator assembly forwards, second role is to provide structural support to a rather long, thin rod which is highly brittle and is susceptible to snapping when a explosive force pushes it from an end . However one key point to note is that majority of the KE imparted by propellant charge will be wasted in propelling the Sabot minus the penetrator iow it is important to keep the mass of the Sabot as low as possible . DU's Young's modulous is lower than that of Tungsten and that is why it is more prone to snapping under loads/stresses along it's length and hence the need for a bigger Sabot to support the penetrator.Having said that This low elasticity is a good thing to have during the event when penetrator meets the target as DU rod tip does not mushroom out unlike Tungsten tip and instead undergoes ablation so it remains sharper and hence exhibits higher RHA figures for penetration , key thing to note is since it requires a heavier Sabot that advantage is partly neutralized .

^ In light of above it now makes sense as to why Ru based penetrators have small Sabots and need to have larger bore riding fins .
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by rohitvats »

I've converted my write-up on APFSDS scenario into blog post.

http://vatsrohit.blogspot.in/2013/11/in ... io-ke.html

Will convert this into article for BR as well.

I've edited the blogpost to rearrange the material on Primer on APFSDS as well as add some more material on this aspect.
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by Leo.Davidson »

rohitvats wrote:I've converted my write-up on APFSDS scenario into blog post.

http://vatsrohit.blogspot.in/2013/11/in ... io-ke.html

Will convert this into article for BR as well.
Awesome. Quite articulate.
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by member_22872 »

matrimC:
BRL has an open source CAD software called BRL-CAD (it uses different solid modelling techniques than those in commercial modeling tools like Solid Works for example). That said, they are secondary to the Analysis engines - statics (ANSYS, NASTRAN) and dynamics (LS-DYNA is the preeminent code but is explicit which have advantages disadvantages vis-a-vis implicit codes).
another open source with capability to mesh is salome. They use OpenCASCADE technology, very good. Another thing is recently MSC is coming up with Meshless solvers using Reproducing Kernel based Particle methods (or variants) , they can simulate beyond continuous regimes and are good for studying fracture mechanics.
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by Vayutuvan »

SaiK
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by SaiK »

well compiled rohitvats! let the force be with you.
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by Rien »

Excellent work . How did you get expert in this area? Was it just a lot of time and reading, or what did you have to do? One question I still have though, how does the DRDO produced rounds compare to other rounds internationally, including Chinese, Pakistani, Russian and US? From the description, it seems that Bharat only has tungsten rounds whichare less effective than Pakistan's U238 rounds. Is that true or not? How does it compare to China's?
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by rohitvats »

Rien wrote:Excellent work . How did you get expert in this area? Was it just a lot of time and reading, or what did you have to do? One question I still have though, how does the DRDO produced rounds compare to other rounds internationally, including Chinese, Pakistani, Russian and US? From the description, it seems that Bharat only has tungsten rounds which are less effective than Pakistan's U238 rounds. Is that true or not? How does it compare to China's?
Thank you for the good word.

However, I'm hardly any expert on the subject of KE rounds. My inquiry into the subject was from the angle of our domestic capability in this segment as well over all picture. And where are we headed. That is something which I gathered after reading on material available on the net. With some details about the technological level in the country.

Having said that, the study of technical aspect of KE rounds like their performance and characteristics required familiarity with certain knowledge base which I frankly don't have. I've read some literature on the subject but there is a limit to which I can go. And write about or comment.

There are other more technically qualified people with right background (engineering as well as Masters/Phd in science) on this board who can comment on this aspect.
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by Rien »

rohitvats wrote:
Rien wrote:One question I still have though, how does the DRDO produced rounds compare to other rounds internationally, including Chinese, Pakistani, Russian and US? From the description, it seems that Bharat only has tungsten rounds which are less effective than Pakistan's U238 rounds. Is that true or not? How does it compare to China's?
There are other more technically qualified people with right background (engineering as well as Masters/Phd in science) on this board who can comment on this aspect.
My reading on this topic unearthed this titbit, which looks bad

http://en.wikipedia.org/wiki/Lion_of_Babylon_%28tank%29
The Lion of Babylon was outclassed by the M1 Abrams, the Challenger 1/2 and by any other contemporary Western main battle tank during the 1991 Persian Gulf War and the 2003 invasion of Iraq.[14] For example, a 120 mm depleted uranium (DU) APFSDS round from an M1 could knock out an Asad Babil tank well beyond 3,000 m,[15] while the effective range of a tungsten-core 125 mm shell is scarcely 1,800 m.
So since the Pakistanis do field U238 rounds, they can kill a T-90 while a T-90 can't kill a T-80.

http://www.acig.org/artman/publish/article_4.shtml
6). A new 125 mm anti-tank DU round called Naiza was being displayed (including some other DU rounds by other Pakistani companies) by Al-Technique. The Naiza is said to have a penetration of 550 mm in RHA. It has been made compatible with T-80UD tanks.
Now this doesn't mean much necessarily. There are at least half a dozen ways to kill a tank. Nag, Helina, Rudra and RPG's and Javelin just off the top of my head. But in tank vs tank battles does T-80UD have the ability to kill a T-90?
Everything I've read says U238 rounds are better long ranged rounds that can kill from further away than a tungsten round.
Difference between a sniper rifle and a normal rifle.
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Re: Project BRF - Indian APFSDS Ammunition Scenario

Post by Singha »

not AP, but DRDO has now tested two new shells for arjun tank in chadipore on a target tank - HE and thermobaric.

http://english.mathrubhumi.com/news/ind ... s-1.786946
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