Sciencemadness Discussion Board - Military Munitions - Exotic Primaries

Military Munitions - Exotic Primaries

Farnsworth - 4-11-2012 at 16:48

I have a question that has been bugging me. I do ask that this topic not specifically segue into anything of the "applied chemistry" nature, but I can't really make sense of this.

Artillery shell impact fuses.

You mean to tell me that there is a class of primary explosives that is so shock resistant that it can be fired out of a cannon at thousands of g's worth of acceleration by exploding smokeless powder, be subjected to atmospheric heating through the shell body, resist rough handling in transport, and in come cases even withstand the stock of initial impact to detonate within a target?

Obviously the answer is yes, because those things happen every day whenever military munitions get used.

But what on earth kind of magical chemistry is going on in there? It would sure as heck seem to be something beyond the realm of your typical lead azide.

bobm4360 - 4-11-2012 at 17:11

It's mostly mechanical engineering! The primer pellet is well insulated inside the fuze, and is dense enough so there is no internal friction in the pellet. Davis,"Chemistry of Powder & Explosives" will give you the chemistry, and any older edition of TM9-1300, "Ammunition, General" will give you an idea of the mechanical workings. Arty fuzes are easy-20mm fuzes-now that's engineering!

Regards,
Bob

caterpillar - 5-11-2012 at 04:18

Moreover, the largest acceleration occurs not within gun's barrel, but when an anti-tank shell penetrates aforementioned vehicle's armor (or a large caliber shell penetrates a battle ship's armor). Many of such shells did not exploded at all.

Ral123 - 5-11-2012 at 05:41

So the impact with the armor doesn't set off the main, that's very simple-I'd suggest TNB/HMX-PBX with like 20% inerts. But it shouldn't set off the booster too, lest say the same mixture but with less density. But the rest of the "explosive train" I can't imagine.
And how is the ignition of a bazooka so precise, in nuclear bombs it's so easy, they use EBW or ''slapper detonator'' sometimes powered by explosively pumped flux compression generator. But how they stuff precise ignition in a bazooka?

Farnsworth - 5-11-2012 at 07:25

Bazooka rockets actually use standard detonators. Because the shell is actually rocket-powered, it has less of a sharp acceleration curve compared to a cannon. Zee Germanz, in the Panzerschreck (bazooka copy scaled up bigger), used mercury fulminate with a Tetryl booster IIRC. No idea what our bazooka used, but probably something similar.

Ral123 - 5-11-2012 at 08:16

Strange, an explosive booster in a rocket, but how is it ignited?

Farnsworth - 5-11-2012 at 08:38

Without getting too practical, there was a mechanism involving a percussion activated pyrotechnic squib and a weighted firing pin with a setback spring.

Melmoth - 8-11-2012 at 10:10

The bazooka youre referring to is a ROCKET, HIGH-EXPLOSIVE, 3.5-INCH AT, M28A2.

Quote:

When the rocket is fired, the force of inertia causes the setback sleeve to move rearward. It is held in its rearward position by the lockpin. When the rocket leaves the muzzle of the launcher, the ejection pin is thrown clear of the fuze by the ejection pin spring. The fuze is then fully armed. During flight, tie firing pin lever and firing pin spring prevent the firing pin from striking the detonator, The creep spring retards the forward movement of the plunger and actuating sleeve. The action of the creep spring prevents the fuzefrom firing should the rocket strike light objects such as thin brush or undergrowth. e. Upon impact with a more resistant object, the plunger and actuating sleeve move forward until the sleeve hits the firing pin lever. This causes the firing pin to strike and detonate the warhead.

Simple weaponry mechanics

[img]http://www.bocn.co.uk/vbforum/attachment.php?attachmentid=33565&d=1277494991[/img]

[Edited on 8-11-2012 by Melmoth]

grndpndr - 8-11-2012 at 15:20

Quote: Originally posted by Melmoth

The bazooka youre referring to is a ROCKET, HIGH-EXPLOSIVE, 3.5-INCH AT, M28A2.

Quote:

Simple weaponry mechanics

[img]http://www.bocn.co.uk/vbforum/attachment.php?attachmentid=33565&d=1277494991[/img]

[Edited on 8-11-2012 by Melmoth]

Not To be snide but have you ever heard of a mechanical minimum detonation distance and piezo electric fuzed AT rifle grenade,bazooka etc?Not to mention the arming delay of artilleryThe forerunner of the 3.5in bazooka
the 2.36in bazooka incorporated a combination mechanical/piezoelectric fuze.When the projectile was fired be it RG,bazooka etc. an inertia activated setback leaf delays alignment of the detonator with the with the booster.When the projectile strikes the target a piezoelectric crystal in the sheet metal nose is stressesd (crushed)generating an electric impulse to the detonator initiating the explosive train.

1. Inertia setback causes the first of the three setback leaves in the setback leaf assembly to overcome the tension of its spring.
2. Setback leaf number 2 rotates releasing setback leaf #3.
3.Setback leaf number 3 rotates releasing a rotor assembly containing the ring circuit.
4. The rotor assembly turns 90 degrees to close the firing circuit thus arming the grenade
5. Upon impact with the target the lucky (piezoelectric) fuse is
stressed generating an electrical impulse
6. The electrical impulse passes thru a resistance wire in the Rotor the detonator initiating the explosive train.

Every weapon Ive encountered up to 155mm howitzers , to 40mm grenade launchers have a positive fail safe delay built into the fuse assembly for safetys sake preventing detonation until a safe distance is reached.The only exception Im aware of is the hand grenade,rifle and MG's.Cannon and howitzer fuses as well as the 40mm GL operate on the principle that the projectile/fuse assembly must rotate a certain # of times after firing from the rifled bore before the fuse is armed which equals a certain safe distance.Think of the danger of carrying in combat a fused explosive projectile w/o some sort of certain mechanical safety delay.Somewhat akin to a grenade without a 4sec delay. As an example the 40mm GL has a mimimum fuse arming distance of 45-90 ft before which it cannot detonate save for some catastrophic event, further than the wounding radius of the grenade in question.As well the M72 Light Antitank Weapon has a minimu7m arming distance of 10meters.
Whats described sounds like an improvised weapon or the FP system on a .45 automatic and Im sure other weapons using hammer provided inertia w/a spring loaded FP to fire the primer.

TM-1330-200
landmine warfare
FM 23-3
[Edited on 8-11-2012 by grndpndr]

[Edited on 8-11-2012 by grndpndr]

[Edited on 9-11-2012 by grndpndr]

Motherload - 8-11-2012 at 21:54

From what I understand ..... There are 3 spring loaded weights blocking the firing pin. The spring tension and mass are critical and are the deciding factor for the arming distance of a HE projectile.
The centrifugal force generated upon firing through a rifled barrel moves the weights to a locked (armed) position allowing the firing pin to actuate the primer upon impact.
Simple in theory but complicated in reality.
Rocket propelled munitions have a similar system as the stabilizing fins provide the necessary rotation (centrifugal force) to arm it.
However ... I do not believe the RPG series and older munitions like the M202 and the panzerfaust to have such a safety mechanism.

[Edited on 9-11-2012 by Motherload]

Ral123 - 8-11-2012 at 22:01

And what if the enemy is in bushes or something? The "piezo-fuze" will make the weapon useless, unless you hit someone's head. And what kind of primary explodes reliably by high voltage? I cant make even "large" lead azide crystals explode from a high voltage spark.

Motherload - 8-11-2012 at 22:21

Given the amount of kinetic energy in the warhead .... It doesn't take a hard surface to set off the fuze.
Just like a lead nail won't under any normal conditions won't penetrate a block of wood, no matter what hammer is used, but ..... When fired out as a .22 LR .... Even though its doesn't have sharp edge ..... But with pure KE it penetrates the block of wood.
This is just an analogy ... KE changes many things.

AndersHoveland - 9-11-2012 at 01:41

The latest detonation technology is electrically triggered, and uses an exploding filament to initiate the primary. This has the advantage that a less sensitive safer primary can be used. Where safety is important, a "slapper" type arrangement is used, where the exploding wire filament drives a metal plate that compresses an explosive against another plate, with the plate so arranged that it focuses pressure on a concentrated area. Even with relatively insensitive explosives, it is not difficult to induce detonation since a a small quantity is being suddenly compressed and abiotically heated at a pressure point.

One of the older designs for bombs contained both the primary and main explosive in the same housing, but the primary was positioned in such a way that, even if it went off, it would be unable to initiate the main explosive in the absence a booster charge. The bomb contained a small easy to access panel, from which the booster charge module could easily be inserted just prior to the bomb being dropped. This apparently had the advantage that the flight crew did not have to directly handle sensitive detonators in flight, and the fact that the primary was already inserted into the bomb before flight also reduced the risk of accidental detonation. Most of the bombs used a mechanical spring hammer to trigger the primary. Just the impact alone of falling from such a height was often enough to cause the bombs to explode, but the trigger ensured reliability.

[Edited on 9-11-2012 by AndersHoveland]

grndpndr - 9-11-2012 at 03:52

Quote: Originally posted by Ral123

And what if the enemy is in bushes or something? The "piezo-fuze" will make the weapon useless, unless you hit someone's head. And what kind of primary explodes reliably by high voltage? I cant make even "large" lead azide crystals explode from a high voltage spark.

What a confused bunch of notions!Apparently some havent yet gotten the word electric detonators have been perfected
to a satisfactory level for use in munitions. Has anyone bothered to look into a field manual at the actual design of the fuzes of RPG's,bazookas,rifle grenades.By the way there are many orders of magnitude between the kinetic energy of a projectile fired from a cannon @ some 2500 FPS Minimally compared to that of an RPG traveling at a few hundred FPS so those cannon fuses are not comparable to the slow moving projectiles of a bazooka,RPG and similar weapons. In the main I believe HV projectile fuses are mechanical but the do contain delay mechanisms as described.Low velocity RG's ,RPGs,Bazooka fuses also contain delay mechanisms.
I provided some frield manuals with specific design and performance detail containing designs of these weapons but its quite obvious
no one bothered to research thier designs.Before you criticize perhaps you should take some time to do some research.In other words please use the FSE.

I have no Idea about the panzerfaust fuse mechanism it mostv likel did contain an inertia FP to initiate the detonator /booster but the panzerfaust wasnt designed with user safety in mind.Cost,effectiveness and use of strategic materials were far more important than some 16yr old hitler youth's life
lost to premature detonation.

[Edited on 9-11-2012 by grndpndr]

grndpndr - 9-11-2012 at 04:21

I just got of the done researching piezoelectric fuses for a few minutes.
If In doubt take a few minutes from your preconceptions
and learn something.Although this is updated ww2 technology the modern US AT4,84mm carl gustav RR ,RPG,among many others still utilize the piezoelectric fuze in thier HEAT warheads.Take a look! Whats not to like with the Lucky fuse?Almost instantaneous electrical action compared to inertia FP,several safety features
not to mention some 70 yrs of successful use.

As QS is rightly quick to point out lets see the documentation!
I showed you some of mine, lets see yours rather than silly hide behind bushes opinions etc.?

[Edited on 9-11-2012 by grndpndr]

[Edited on 9-11-2012 by grndpndr]

Farnsworth - 9-11-2012 at 19:57

Picture is a cutaway of an antique M6 bazooka rocket, with the detonator assembly visible in the base of the warhead section (yellow stuff) just for reference.

franklyn - 10-11-2012 at 14:16

Fundamentals of Ammunition
http://www.tngun.com/wp-content/uploads/2011/10/MM0144-Fundamentals-of-Ammunition.pdf

Ammunition General TM-9-1300-200
http://www.liberatedmanuals.com/tm-9-1300-200.pdf

Engineering Design Handbook - Fuzes AMCP 706-210
http://www.dtic.mil/dtic/tr/fulltext/u2/889245.pdf

Engineering Design Handbook - Explosive Trains AMCP 706-179
http://www.dtic.mil/dtic/tr/fulltext/u2/777482.pdf

Ordnance Explosive Train Designers Handbook , 48 MB
http://www.dtic.mil/dtic/tr/fulltext/u2/029151.pdf

Engineering Design Handbook - Timing Systems and Components AMCP 706-205 , 34 MB
http://www.dtic.mil/dtic/tr/fulltext/u2/a020020.pdf

Proceedings of the Symposium on Electroexplosive Devices (6th) , 33 MB
http://www.dtic.mil/dtic/tr/fulltext/u2/720455.pdf

Engineering Design Handbook - Terminal Ballistics Kill Mechanisms AMCP 706-160
http://www.dtic.mil/dtic/tr/fulltext/u2/777482.pdf

Engineering Design Handbook - Terminal effects AMCP 706-245
http://www.dtic.mil/dtic/tr/fulltext/u2/389304.pdf

The Radio Proximity Fuze
http://www.smecc.org/radio_proximity_fuzes.htm

Optical and Magnetic Fuzes
http://www.smecc.org/optical_and_magnetic_fuzes.htm

http://www.sciencemadness.org/talk/viewthread.php?tid=10575&...

http://www.sciencemadness.org/talk/viewthread.php?tid=10575&...

.

[Edited on 10-11-2012 by franklyn]

Melmoth - 13-11-2012 at 10:46

@grndpndr I think you've got youre rockets mixed up a WW2 bazooka rocket 2,36" doesnt have a piezo electric fuze. The fuze was a very simple impact type. Once the safety pin was removed, the weighted striker was held only by the light creep spring. Once armed, the round would detonate if dropped on its nose from about shoulder level. It's electricaly fired though. RPG7 series have piezo-electrical fuzes VP7

@motherload rocket propelled munitions have seldom centrifugal safety measures. The panzerfaust fuze (FPZ8001) relies only on a mechanical setback safety.

grndpndr - 13-11-2012 at 15:45

You seem to be correct as I couldnt find any reference to the 2.36 bazooka ever being retrofitted with an improved PIBD fuse.(And Im not that old to have any FMs/TMs referencing the M1A or improvements LOL) I may have confused the M31 RG with the same wARhead as was used
with the 2.36 in M1a.I believe that instead the 2.6in M31 warhead was the basis of the original warhead for the 66mm M72 Law introduced in early 60s along with the russ RPG7.
I did however read of the many problems with the original mech fused 2.36 bazooka including the bad habit you mentioned of detonating if dropped with safety removed.Or perhaps worse not detonating when desired. Such as an extreme oblique angle(glacis plates) ,long range soft targets (Sand mud).Which may not sound important for an AT wpn but after action reports
indicate the bazooka was used much like the M72 LAW is today against bunkers,Fighting positions,breaching concertina,masonry.As an aside I read a report about the 2.36 bazooka versus T34 in Korea.Task Force Smith tasked with stopping an armored column early in the war an american officer allegedly fired some 20+ rockets into the rear engine compartment area of a single T34 w/o effect!?I find that remarkable as obviously that is the thinnest armor on any tank.In the case of the T34 it could have been as thin as 3/4
in or thick as the 3.5 in glacis plate.Believe it or not story I didnt read the story in the form of an official after action report found in TMs etc.Could very well be in the heat of the moment 2 seemed like 20 and seconds- hours.

PS As for the 3.5 "superbazooka" that was rushed to korea
(a remarkable story in itself)I believe they were equipped with the M20 A1 Rocket which also had a mech fuse.Whether the PIBD fused M28A1 came into service late korean war or was a postwar munition I havent found the answer to.

[Edited on 14-11-2012 by grndpndr]

[Edited on 14-11-2012 by grndpndr]

[Edited on 14-11-2012 by grndpndr]