Stryker photos

[MordeanGrey]

I noticed another thread recently that mentioned the stand-off armored Strykers.

I found these photos at http://www.strykernews.com/gallery/

There are many more photos there.

[MordeanGrey]

Another view

[TKTM]

They should change the name to "the strainer"

[MACV]

Whats with the wrought iron fence surrounding it?

[TKTM]

It rips the tail fins off of RPG's, and basically renders them ineffective.

[andresere]

RPGs are PIBD (point initiated, base detonating). If you make them pop early, it keeps them from impacting the armor. Most shaped charge warheads can be defeated by use of "stand-off" armor. Shermans during WW2 used chicken wire to do the same thing to Panzerfaust rounds.

[Mike Veldhuisen]

Thbe russians also used bed springs to detonate shaped charge warheads before they could impact the main armor.
mike

[gman552]

Here's an excellent page from a site dealing with WW2 German shaped-charge munitions and methods of defeating them:

http://www.geocities.com/Augusta/8172/panzerfaust1.htm

[dadman]

Underneath all that livestock fence, it's still an expensive Stryker.

[19kilo]

Originally posted by andresere
RPGs are PIBD (point initiated, base detonating). If you make them pop early, it keeps them from impacting the armor. Most shaped charge warheads can be defeated by use of "stand-off" armor. Shermans during WW2 used chicken wire to do the same thing to Panzerfaust rounds.

It either blows them up far enough away to prevent them from hitting the armor OR it can actually "catch" them in the fencing and then they do not even detonate!
Also, from what I have read; the Stryker's ceramic plate armor (made in Germany) has a better chance of withstanding a hit from an RPG-7+ than the Bradley does. Not that the Bradley is a tank or anything to write home about.

Cheers.
KILO OUT

[EMDII]

Originally posted by TKTM
It rips the tail fins off of RPG's, and basically renders them ineffective.

Not really so. andresere has the facts: PIBD is used to initiate a molten stream/plasma from a shaped charge using the so-called Munroe Effect. The standoff triggers the PIBD, and the plasma is dispersed and cooled over the extra distance, reducing significantly the likelihood of penetration.

Yes, Weapons Systems Engineering is my specialty.

[xtremerange]

Put some canvas on it and see if it floats in the English Channel.

[Rooster]

I wonder how one of those would handle in a traffic jam. Could you roll over the other cars?

[TKTM]

Originally posted by EMDII


Not really so. andresere has the facts: PIBD is used to initiate a molten stream/plasma from a shaped charge using the so-called Munroe Effect. The standoff triggers the PIBD, and the plasma is dispersed and cooled over the extra distance, reducing significantly the likelihood of penetration.

Yes, Weapons Systems Engineering is my specialty.

That certainly is a possible mechanism, the other is to destabilize the projectile so that when it hits, the shape charge is set askew.

[1gewehr]

RPG rockets are about 18" long with the fins at the extreme rear. In order to catch the tail fins before impact, the stand-off armor would have to be at least 18" from the hull. The Stryker stand-off system is only about one foot from the hull in some places. Thus, catching tail fins would be useless if a rocket hits there. Ooops.
1gewehr

[TKTM]

Originally posted by 1gewehr
RPG rockets are about 18" long with the fins at the extreme rear. In order to catch the tail fins before impact, the stand-off armor would have to be at least 18" from the hull. The Stryker stand-off system is only about one foot from the hull in some places. Thus, catching tail fins would be useless if a rocket hits there. Ooops.
1gewehr

AND I QUOTE FROM DefenseLINK news " It is slats placed about 18 inches away from the main body." . So would that be a double OOPS ?

[GunWares]

I don't know why, but with the standoff armour the vehicle reminds me of Hannibal Lecter in "Silence of the Lambs." Maybe they should have named it the "Lecter."

[EMDII]

Originally posted by TKTM


That certainly is a possible mechanism, the other is to destabilize the projectile so that when it hits, the shape charge is set askew.

The gaps are narrow enough to force a detonation early. No 'askew' to it. Go ask someone else who knows TK- this is what we do. See the spacing between the slats: too narrow for an RPG warhead to pass through. The RPG body is either 85mm (AT) or 70mm wide at the join of the two cone-shapes. The slats trigger the weapon early, or damage the body, or WTF. But they are NOT 'fin-traps', OK.

[TKTM]

Originally posted by EMDII


The gaps are narrow enough to force a detonation early. No 'askew' to it. Go ask someone else who knows TK- this is what we do. See the spacing between the slats: too narrow for an RPG warhead to pass through. The RPG body is either 85mm (AT) or 70mm wide at the join of the two cone-shapes. The slats trigger the weapon early, or damage the body, or WTF. But they are NOT 'fin-traps', OK.

h
I think a wise engineer would design with both priincipals in mind. That said, of the reports I was able to find, 1 indicates the method you mention, the other indicates that it functioned as I mentioned. But no doubt when the army "explains" how they work, they list "your" method.

[19kilo]

Originally posted by TKTM

h
I think a wise engineer would design with both priincipals in mind. That said, of the reports I was able to find, 1 indicates the method you mention, the other indicates that it functioned as I mentioned.

It is obvious that 1 of your reports is incorrect as to the function of the stand off armor. I will give you three guesses as to which one is correct...your first 2 guesses don't count.

After contacting the screening material - hell they could have used a chain link fence for the same outcome - the warhead (which WILL NOT PASS THROUGH THE SLATS) is either detonated or caught by the fencing material. Since the warhead WILL NOT PASS through the fence...it is very difficult nay; impossible, for it to lose its fins and wander off course hitting a nearby goat or camel instead of the body of the vehicle!

Cheers.
KILO OUT

[eodinert]

Kids! Don't make me stop this car.

Ok, here's the deal.

The RPG is electrically fired (the warhead, not the projectile). In the nose is a piezoelectric element. It generates an electric charge when it whacks something. In the base of the warhead is a fuze, sort of. It's more like a switch: When the rocket is fired, setback puts the switch in the 'on' position. This enables the electricity from the piezoelectric thingy on the front to energize the electric blastic cap at the base of the warhead. There is also a pyrotechnic delay/self destruct mechanism in the fuze, but that's not really relevent to this discussion.

'Well, how do the electricity get from the piezo electric thingy to the blasting cap?'

Glad you asked. The RPG has inner and outer aluminum cones that are insulated from one another. The electric current travels through the inner cone in the windshield, through the shaped charge cone itself to the electric initiator. The outside of the warhead serves as a conductive path, as well.

'What does this have to do with anything?'

Well, when the RPG hits the 'slat' armor of the stryker, one of two things will happen. It will strike between the slats, or it will hit a slat.

If it strikes between the slats, the piezo electric thingamabob won't make an electricity, and the inner and outer conductive cones are shorted together, shorting the path for any possible electric current that probably isn't there anyway. Also, since it's hauling ass (about 900 fps), and made of thin aluminum, it will in all likelyhood 'come from together', and scatter itself about in many pieces and be mostly not harmful.

Result: No detonation.

If it hits the slat, it will function as designed, but the standoff is waaay off (standoff: the optimum distance for a shaped charge to work, which just happens to be the distance from the piezo electric element to the shaped charge in this case) and the 'jet' will be deflected and diffused by the slat armor.

Result: Detonation, but seriously reduced effectiveness.

Having said all that, here's a picture to clarify things and make visible all those tidbits that I so eloquently described above:



You can see a white plastic insulator near the nose, the silver inner cone/cuductive path, and a brown bakelite insulator near the major diameter where the strap holds the cutaway down to the plaque. This is the weakness the slat armor is designed to exploit.

Edited to add: Everything south of the 'warhead' is not relevent to the explosive effect (shaped chared/monroe effect etc), it's just the ride that gets the warhead to the scene of the armor...Also, a PG7 from stem to stern is about 37 inches configured for flight... fins show up about 30 inches from the nose

Questions?
~Doug

[dadman]

Originally posted by eodinert
Kids! Don't make me stop this car.

Ok, here's the deal.

The RPG is electrically fired (the warhead, not the projectile).
~Doug

You said a mouthful that is easy to comprehend.
Question:
At 900fps, would the projectile/warhead have enough energy/force to go through other types of add-on armor such as chain-link, sandbags, or welded-on plate?

[EMDII]

400 fps is it's launch velocity: it acceleraes after that to ~ 900 fps. They are surprsingly incapable of ballistic penetrations: they arew slow, have a large surface area, and they don't really need speed to "make way"! The warhead is velocity-insensitive: if the warhead works, you get a plasm jet that WILL drill 600m of RHA (rolled homogenous armor).

It's not about velocity: it's about the warhead.

Shaped Charge
The discovery of what is variously referred to as the shaped charge effect, the hollow charge effect, the cavity effect, or the Munroe effect, dates back to the 1880s in this country. Dr. Charles Munroe, while working at the Naval Torpedo Station at Newport, Rhode Island, in the 1880s, discovered that if a block of guncotton with letters countersunk into its surface was det-onated with its lettered surface against a steel plate, the let-ters were indented into the surface of the steel. The essential features of this effect were also observed in about 1880 in both Germany and Norway, although no great use was made of it, and it was temporarily forgotten.

A shaped charge warhead consists basically of a hollow liner of metal material, usually copper or aluminum of conical, hemispherical, or other shape, backed on the convex side by explosive. A container, fuze, and detonating device are included.

When this warhead strikes a target, the fuze detonates the charge from the rear. A detonation wave sweeps forward and begins to collapse the metal cone liner at its apex. The collapse of the cone results in the formation and ejection of a continuous high-velocity molten jet of liner material. Velocity of the tip of the jet is on order of 8,500 meters per sec, while the trail-ing end of the jet has a velocity on the order of 1,500 meters per sec. This produces a velocity gradient that tends to stretch out or lengthen the jet. The jet is then followed by a slug that consists of about 80% of the liner mass. The slug has a velocity on the order of 600 meters per sec.

When the jet strikes a target of armor plate or mild steel, pressures in the range of hundreds of kilobars are produced at the point of contact. This pressure produces stresses far above the yield strength of steel, and the target material flows like a fluid out of the path of the jet. This phenomenon is called hydrodynamic penetration. There is so much radial momentum associated with the flow that the difference in diameter between the jet and the hole it produces depends on the characteristics of the target material. A larger diameter hole will be made in mild steel than in armor plate because the density and hardness of armor plate is greater. The depth of penetration into a very thick slab of mild steel will also be greater than that into homogeneous armor.

In general, the depth of penetration depends upon five factors:
Length of jet
Density of the target material
Hardness of target material
Density of the jet
Jet precision (straight vs. divergent)

The longer the jet, the greater the depth of penetration. Therefore, the greater the standoff distance (distance from target to base of cone) the better. This is true up to the point at which the jet particulates or breaks up (at 6 to 8 cone diameters from the cone base). Particulation is a result of the velocity gradient in the jet, which stretches it out until it breaks up.

Jet precision refers to the straightness of the jet. If the jet is formed with some oscillation or wavy motion, then depth of penetration will be reduced. This is a function of the quality of the liner and the initial detonation location accuracy. The effectiveness of shaped charge warheads is reduced when they are caused to rotate. Spin-stabilized projectiles generally cannot use shaped-charge warheads.

From the USMC AT-4 manual

e. Functioning. The AT-4 has a 3.96 pound warhead with a shaped charged. (See Figure 3.)
(1) Penetration in excess of 17.7 inches is due to the shaped charged munroe effect.
(2) When the rocket travels 10 meters from the muzzle the detonator is in line with the explosive train.
(3) The fuze is activated by a piezoelectrical crystal, which on impact generates an initiation voltage, even at an angle of impact as shallow as 10 degrees, detonating the shaped charge.

Piezoelectrics and you-

Inside a grenade AND your grill...
Certain crystalline materials (like quartz, Rochelle salt and some ceramics) have piezoelectric behavior. When you apply pressure to them, you get a charge separation within the crystal and a voltage across the crystal that is sometimes extremely high. It turns out one of your household appliances uses similar technology: In a grill starter, the popping noise you hear is a little spring-loaded hammer hitting a crystal and generating thousands of volts across the faces of the crystal. A voltage this high is identical to the voltage that drives a spark plug in a gasoline engine. The crystal's voltage generates a spark large enough to light the gas in the grill. This same kind of technology can be used to detonate grenades and warheads.

BTW, if the thugs are using RPG-2 systems, they have no sustainer motor. Coast all the way.

Daddy, are we there yet




And yes, this IS rocket science.

[Firestarter]

The effect on a target from the jet is alot like what a stream of water does when squirted into a bank of dirt. Material that is dislodged at the deepest part of the hole turns to mud and flows back along the walls of the hole.

When the mesh around the vehicle or some sort of trap causes a "standoff" it affects the plasma jet because the particles hit further apart from a central point and not contributing to the penetration at the center of the target. Imagine the same stream of water coming from a high pressure hose. If you were to adjust the nozzle just a bit where you start to have a spray rather than a stream the erosion of the hole is decreased because there is no concentrated area that is working against this target material.

Also after the jet has formed there is a type of heavy slug of remaining material that follows the jet at a much slower rate of velocity.

However although if too far away the jet will start to break up reducing the effectiveness of the charge, the effectiveness can be affected if the detonation occurs to close to the target because the jet has not had time to form.

With conical charges there is an optimum distance for the detonation to occur for maximum penetration of the target material. This is what the term "standoff" means and is expressed in terms of "charge diameters".

Now if EMD starts graphing out Rayleigh lines and Hugoniot values and such then this thread has really gotten way too deep! HaHa!

[EMDII]

Originally posted by Firestarter
.....
Now if EMD starts graphing out Rayleigh lines and Hugoniot values and such then this thread has really gotten way too deep! HaHa!

Those theorems seem used most often in aerodynamics and large flow models. I haven't used them at all, although we had heard of such modelling in 974 when I started my senior research project at USMA.

[TKTM]

eodinert, Thanks I stand corrected

Looking at the info, riping the fins off seems like the least like avenue of defeat in this particular system. It would appear that the slats are "sturdy" enough, to rip apart the warhead. Although, I had earlier seen stryker photos were the slats had been bent apart as if an RPG had pushed between them. But, now I wager that RPG detonated between the slats and pushed them apart. I had also read reports, that RPG's had made it through the slats but were sent askew. When I reread the reports, the stated that it was actually parts of the rpg, and not the whole head (although, Im sure how they drew the parts conclusion). So, I wager the primary mechanism is to disrupt the warhead, actual detonation of the piezo device is secondary. Ripping off the tail fins is probably the last viable method. It is interesting though, I have some armies using cyclone fencing to accomplish just that feat, rip the tail fins off, send the warhead askew.

[EMDII]

A popular fix in RVN was to stretch chain-link around the Sheridan and other AFVs. When working the jungle, the range was so short that it was difficult to suppress the shooters. The chain-link sometimes detonated the weapon (if it had armed beyond minimum range), and sometimes the weapon just stuck, usually broken from the impact.

The warhead is too large to pass through the fence material grid, and the fence's flexibility makes a rather 'soft' catch. Quit effective as a disabler of the RPG warhead. It could be very unnerving to AFV crew to get out and find several RPG warheads 'suspended' in the mesh.

[RRotz]

Dud RPG's did penetrate the doors of Deuce and a half's and impale themselves into troopers. One driver was killed that way in Col. McKnight's convoy.

Great discussion! Aren't shaped charges devilishly evil? If the plasma jet of molten metal (of your own vehicle) doesn't get ya, the spall will spray ya good!

[TKTM]

The one I want to hear about is the "secret weapon" that took out the Abrams tank. Pencil eraser size piece of yellow metal shot through the armor on one side, passed through a crewmans vest (kidney area, did not hit crewmen though) went through some equipment and buried itself about 1.5 inches deep in the armor on the otherside. The story made the news for awhile, but I never heard what the result of the "investigation" was.

[EMDII]

We posted it here, including material I got from Fort Know. the entire vehicle is NOT armor, DU, or armor plated. the round entered an area sort of like a golden BB. No release on the actual warhead, but some speculate it was an RPG-18, RPG-22, or RPG-29.

RPG-22 72mm
A scaled-up version of the RPG-18, the RPG-22 has improved performance and was introduced in 1985. It is the current issue disposable Russian LAW. Usually issued one per squad. The RPG-22 has an 8-yard backblast (4d6 flame damage).

RPG-29 Vampir 105mm
This Soviet/Russian medium antitank weapon features a folding bipod to assist aiming during prone firing. Iron, optical and night sights are available. The launcher can be broken down into two parts which one soldier can carry. The warhead is a 105mm PG-29V tandem HEAT.

There was alsosome specualtion that it was one of the advanced AT-series FSU weapons. Again, my 2d hand info from Skidgel Hall at Fort Knox is 'golden BB'. There were pics and several citations in the old discussions in N/CE about a year ago.

'Pencil-sized' is the typical plasma jet hole made by a weapon using..........

you guessed it, the Munroe effect.

[eodinert]

In another interesting bit of RPG trivia, the rocket motors are rarely destroyed when the warhead fires.

Most of the RPG rocket motors are made of steel (though some are aluminum), and are nearly undamaged after use. In Iraq, my team responded to at least one call where there was a 'dud' RPG stuck in the ground... but it ended up being a nearly undamaged, but expended, rocket motor.

Only the very front of the rocket motor, which will become slightly concave, will show any evidence of a detonation.

I bring this up because I thought initially that perhaps the rocket motor itself could continue through the stryker slat armor once the warhead had detonated, but after some reflection I thing it would go the other way (or the way it had come from). If the warhead did not detonate, the rocket motor would definately continue to march, as they say, and probably wonk the slats a bit.


One of the most ingenious and facinating thing about the PG7 round itself is the way in which it is fired, and the launching itself occurs.

The PG-7 has two 'motors', one that is a traditional rocket, with internal solid fuel and nozzles around the base of the warhead ('sustainer' motor), and the second a 'launch' motor that screws on the rear (makes it smaller for transport) that consists of a paper tube, 40mm in diameter (same as the rocket body/bore of the launcher), with an aluminum fin assembly (tracer on back) and a bunch of propellent that looks like strips of cardboard tied with...string, to the folded fin assembly.

As most people know, the PG-7 has a transverse primer that is struck by the firing pin of the launcher... but that primer does not ignite the sustainer motor, or even a delay for the sustainer motor. It ignites the launch 'motor' (I put that in quotes because it burns so fast as to seem like a detonation) while it's inside of the launcher. 'Setback' or launch forces initiate a short delay, and then the sustainer motor fires about 10 meters downrange.

This is not in itself remarkable, but it is ingenious. What this means is if you are a dumb-ass Iraqi, and you forget to screw on the launch motor and attempt to fire a projectile, the projectile a.), does not launch, and b.), does not sit in the launcher until the sustainer motor fires because it will ONLY fire from setback, which won't happen, 'cause you're a dumb-ass Iraqi and you forgot to screw on the launch motor (The whole point of this complicated, two-part launch system is to negate the possibility of back blast affecting the shooter).

Otherwise, the round could sit in the laucher until the rocket motor fired, blowing the head-rag (and facial features) off the hadji shooting it.

What this ALSO leads me to believe, is that if you drop an new, unfired, safety pinned RPG on it's tail from a height high enough to simulate setback (however high that would be, I don't know), you would initiate the rocket motor (after a short delay) AND arm the fuze, with it's pyrotechnic self destruct mechanism (eight seconds or so then......BOOM!), even without the launch motor screwed on. The 'safety' pin on a PG-7g or m only holds on a small protective cap that covers the piezo electric nose element, and does nothing whatsoever to the fuze itself.

And, if you were wondering, once you attempt to fire the PG-7 without the launch motor, the primer and the 'lead' (or is it 'leade') are expended, and that round will not fire if you then screw a launch motor on it and re-attempt to fire it.

RPG-7's are cool... huhh huh..huh ... huh huh...

Edited to add video:

About this video:
This is a shot looking downrange while an RPG is fired. The sustainer motor kicks in right at the top of the screen.. you can hear it, but it's hard to see. You can follow the tracer down range, until it hits the ground and duds... because RPG's do that... a lot. The self destruct on this one did not work either.

RPG in flight video

~Doug