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A question of grenades and setting them off

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adzling

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« Reply #30 on: (11:07:00/07-15-14) »
Martin, good buddy!
i think you threw a wobbly without appreciating that what I said in my original post was 100% in concordance with what you said.

That's ok, I understand, sometimes it's tough being on the internet.

Any self respecting combat personage in the 6th world would want some very safe grenades strapped to their chests because of fireballs, lightning bolts and what not.

Current miilitary grade explosives are pretty close to being good enough, this entry on RDX one of the most common ones is telling:
"At room temperature, it is very stable. It burns rather than explodes and detonates only with a detonator, being unaffected even by small arms fire. (This is one of the properties that make it a useful military explosive.) It is less sensitive than pentaerythritol tetranitrate (PETN). However, it is very sensitive when crystallized, below −4 C.[citation needed] Under normal conditions, RDX has a figure of insensitivity of exactly 80 (RDX defines the reference point.)."

In the mythbusters episode noted they seem to have shot a two part explosive (yeah i already noted this in a previous post, sometimes you need to restate so people grok what you said), perhaps hitting the detonator (a pencil thin part of the grenade).

Now imagine an electrically detonated version of RDX (or other modern explosive) that requires a specific sinewave pattern to detonate it (so no blasting caps, no lightning bolts, no bullets to set it off).
Hard to imagine?
Not for me given the advancements and pervasiveness of nanotech.

However I do agree with you (and did previously), if your buying 60 year old grenades and they are of the right type a super accurate rifle shot could set one off, but given you are shooting at a pencil sized (or smaller) object embedded in a circular, metal skinned item that is on someone's chest and moving even that scenario is, well, unlikely.

Might as well shoot for the dude's eyeball, it's about the same size.

as always, ymmv.

LionofPerth

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« Reply #31 on: (11:11:49/07-15-14) »
My pleasure, LionofPerth.

As far a so can tell, the books contain no reference to which kind of explosives are used to form the charge of a grenade.

That being said, Arsenal does list a variety of common, real world explosives as being available (TNT and ANFO are good examples), while also expanding upon known variants )like C12).

No chance you got the reply I sent? There were a few more things in it I'd hoped you could help with.
When in doubt, C4.

martinchaen

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« Reply #32 on: (11:33:04/07-15-14) »
i think you threw a wobbly without appreciating that what I said in my original post was 100% in concordance with what you said.
I'll be honest, I have absolutely no clue what you're saying here. My first language isn't English, so you'll have to be a little more concise next time if you want to get your point across.

In the mythbusters episode noted they seem to have shot a two part explosive (yeah i already noted this in a previous post, sometimes you need to restate so people grok what you said), perhaps hitting the detonator (a pencil thin part of the grenade).
I can't speak for the Mythbusters episode as I haven't seen it, but how much do you know about ballistic theory?

Allow me to explain; when a ballistic round (.308 caliber rifle round, for example) penetrates an object (whether that object is a human body or a grenade), the kinetic energy of the round imparts a shockwave through said object. This shockwave is what kills most people who die instantly from a gunshot; it's called shock trauma, and it destroys the tissue surrounding the entry, path, and exit of the round. You don't need to hit someone's heart to cause it to stop beating; a sufficiently powerful round impacting center mass can be enough all by itself. Now, a large part of gunshot wounds do NOT kill instantly, and those who end up dying later on usually do so because exanguination (bleeding out, whether internal or external).

When a relatively large round like the .308 hits the relatively small body of a grenade, there are very few places for the kinetic energy to go; thus, whether you hit the detonator straight on or just hit the composition charge around it, the shockwave will likely be of sufficient energy to set off the primary explosive.

This is fairly basic stuff, and it hasn't changed much in the last 100 years. We've made guns more accurate, capable of firing more rounds in less time, and we've increased caliber sizes (.338, a common rifle round for military snipers these days were developed back in the 80s as far as I know).

Now imagine an electrically detonated version of RDX (or other modern explosive) that requires a specific sinewave pattern to detonate it (so no blasting caps, no lightning bolts, no bullets to set it off).
A secondary explosive (like RDX) still requires a primary explosive to set it off. No matter how much you zap it with a "specific sinewave pattern" RDX still wouldn't detonate, with the possible exception of extremely high voltage and/or amperage (think lightning strike, and honestly, if you can harness the power of lightning to set off a grenade why aren't we just making lightning grenades...).

Look at the explosives section of the Arsenal book; notice how there are still ordinary detonators there? Sure, there are some fancier ones too, but they all have one thing in common; a primary explosive that functions as the "detonator" part of the "[whatever fancy trigger mechanism is used] detonator".

And a primary explosive can be set off by the kinetic energy imparted on a round, such as a .308...

Hard to imagine?
Yes, quite frankly.

What you describe makes absolutely no sense to me. If you want to handwave it with "because X", you might as well just say "because magic", which I personally find to be an insufficient argument. Explosives are real, as are the principles of the physics that apply to them; there is no need to come up with alternate methods when modern day tech is based on principles that are hundreds, if not thousands, of years old.

Not for me given the advancements and pervasiveness of nanotech.
Good for you.

Nanotech would still need to trigger a primary explosive in order to set off a secondary explosive, unless "because nanotech" is a sufficient explanation for why the laws of thermodynamics can suddenly be circumvented to your mind.

It isn't for me, and please try to refrain from pandering quite as much in the future. I see no need for theatrics in a factual debate.


LionofPerth; I'll check once I get home, if I got it I must have overlooked it.
« Last Edit: (11:50:32/07-15-14) by martinchaen »

adzling

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« Reply #33 on: (11:49:58/07-15-14) »
sorry if my odd vernacular threw you, your english is certainly way better than my knowledge of whichever is your mother tongue.

hehe if I can imagine magic then yeah a future tech version of explosive seems, well, easy.

I mean, those magical fireball spells etc aren't tied to the first law of thermodynamics, har!

regardless, whether you agree or disagree that explosives will advance to make them more safe in the next 60 years (much like they did in the past what, 70 years, since RDX et al came on the scene) that's neither here nor there.

let's get back to the meat of this, shooting a pencil you can't see (it's inside something else) with a sniper rifle from what, oh let's say 300 yards while the target is moving.

Now that's something worthy of a miracle!

but then I guess, EDGE.

so hah!

right?



martinchaen

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« Reply #34 on: (11:51:51/07-15-14) »
Again, look above. You just need to hit the grenade; the primary explosive contained in the detonator is sensitive enough to shock that the kinetic energy of a .308 round almost certainly will do it, regardless of whether or not you actually hit the detonator itself, while not being so sensitive that say dropping the grenade on the floor would set it off.

Modern handgrenades are considered relatively safe; there's a reason a lot of soldiers carry them...

Ultimately, my point is this;
There is absolutely no need as far as I'm concerned to invent some new fangled super-explosive that doesn't obey current, known laws of physics, because the published material still references TNT, RDX, Composition explosives, ANFO, blasting caps, radio detonators, and more, all of which exist today. I don't think a single item in the Arsenal book doesn't exist, today with the possible exception of Wireless Detonators and Composition 12 explosives.
« Last Edit: (11:55:15/07-15-14) by martinchaen »

adzling

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« Reply #35 on: (11:56:48/07-15-14) »
well i find sources saying the RDX can't be set off with small arms fire.
so I guess either my sources are incorrect/ not detailed enough OR yours are.

now I'm no explosives expert, I just know how to use the internets.
here's another quote to the one i pasted in before:
"Just as with other explosives, you need to apply some energy to C-4 to kick off the chemical reaction. Because of the stabilizer elements, it takes a considerable shock to set off this reaction; lighting the C-4 with a match will just make it burn slowly, like a piece of wood (in Vietnam, soldiers actually burned C-4 as an improvised cooking fire). Even shooting the explosive with a rifle won't trigger the reaction. Only a detonator, or blasting cap will do the job properly."

if you've got some direct experience setting RDX off with small arms then you've got me there.
I've never fired a bullet at a brick of RDX.
wish I had, but sorry to say I haven't.

;-)
« Last Edit: (11:59:20/07-15-14) by adzling »

martinchaen

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« Reply #36 on: (12:11:59/07-15-14) »
You're correct, RDX can't be set off by gunfire (in my experience, and to my knowledge; I've never fired something like a .50cal or bigger round at some), but you'll note that that's not what I'm saying at all.

I really can't explain it much simpler than this:

A modern day grenade consists of two types of explosives; a relatively unstable primary, and a relatively stable secondary.
The primary explosive is contained in the detonator (ASA compound is often used; mix of chemicals I'm not entirely sure of, though a Google search would probably return the components)
The secondary explosive is packed tightly around the detonator, and in turn surrounded by a metal casing (at least for modern day fragmentation grenade, where the comp B charge is usually 60/40 RDX/TNT with some wax to keep it more stable).
If you hit the grenade with a sufficiently powerful round, the unstable primary explosive is detonated by the shock caused by the kinetic energy of the projectile.
This in turn detonates the stable secondary explosive.

Your quote nails it right on the head; "considerable shock". The amount of shock needed for it to be "considerable" varies with each type of explosive (primary, secondary, or tertiary).

There's a reason EOD robots are equipped with shotguns; the relative kinetic energy contained in each shot is not sufficient to trigger the primary explosive, so you just destroy the shell.

Once again, you're not shooting the grenade to set off the stable secondary explosive (because that wouldn't work), but to trigger the unstable primary explosive (which will in turn detonate the stable secondary explosive).

You said it yourself, you're not an explosives expert. You'll need to do a little more research into ballistics and explosives if the above doesn't make sense to you, because I don't know how else to break it down.
« Last Edit: (12:27:02/07-15-14) by martinchaen »

adzling

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« Reply #37 on: (12:34:44/07-15-14) »
yeah but when you say primary explosive you're talking about the detonator, right?

and that's why i said hitting a pencil sized detonator that you can't see while it's moving with a sniper rifle at range is almost impossible.

but maybe you weren't talking about the detonator?

Reaver

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« Reply #38 on: (12:40:01/07-15-14) »
Note:

The electrical charge of a blasting cap is actually DC, thus, no sinewave......

Now back to the agruement at hand...

<eats popcorn, opens a beer>
Where am I going? And why am I in a hand basket ???

Remember: You can't fix Stupid. But you can beat on it with a 2x4 until it smartens up! Or dies.

adzling

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« Reply #39 on: (13:04:27/07-15-14) »
oh this is most certainly a discussion!

martinchaen

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« Reply #40 on: (13:08:03/07-15-14) »
*sighs*

Listen, no offense, but if you can't understand what I'm trying to tell you above, I don't think we have much more to talk about.

For the last time; you don't need to hit the detonator directly. Hitting the grenade itself is enough, because the energy of the round will travel through the secondary explosive to the primary, thus setting off the unstable part of the grenade which in turns sets off the stable part of the grenade. This isn't rocket science...

What part of this does not make sense to you?
A modern day grenade consists of two types of explosives; a relatively unstable primary, and a relatively stable secondary.
The primary explosive is contained in the detonator
The secondary explosive is packed tightly around the detonator
If you hit the grenade with a sufficiently powerful round, the unstable primary explosive is detonated by the shock caused by the kinetic energy of the projectile.
This in turn detonates the stable secondary explosive.
« Last Edit: (13:09:48/07-15-14) by martinchaen »

adzling

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« Reply #41 on: (14:16:23/07-15-14) »
haha are you sure this isn't rocket science?
I mean some of these explosives are used as rocket fuel....

ok now i get what you're saying, thanks for sticking with me here (i know it's gotta be a pain to be doing this in your second or third language).

i dig it now!

a modern grenade's detonator can be detonated without hitting it itself via secondary concussion by a very high kinetic energy round impacting the enveloping explosive.

cool!

now what happens when you add in 60+ more years of development and crap?
I dunno, i mean how could we KNOW?
all we can do is guess.
and given that RDX did not exist, what, 80 years ago?
then i'd hazard a guess that we'd see some significant safety improvements in the next 60 or so years.

but, as always, ymmv.

thanks for the discussion, it was fun!

LionofPerth

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« Reply #42 on: (14:38:33/07-15-14) »
Short version for those who don't have an understanding of what a bullet does to a body, go find a Mythbusters episode in which you see them shoot a piece of ballistics gel and you get a slow motion shot of it. See the way the bullet trail expands and contracts. That's the wake of the bullet, this is where a whole heap of organ shredding damage is done. It's why you can hit a person, have the bullet out the other side, without actually hitting any organs and still kill. That much velocity produces a lot of energy (Force= mass x velocity, Physics people) and that energy has to go somewhere.

Also physics, as a rule, energy has to go somewhere. In this case, chemical potential energy is turned into kinetic energy and that transfer of kinetic energy, the less said the better.

In the case of a grenade, it doesn't particularly matter how the primary explosive is triggered, be it a chemical fuse or an electrical one, there's still potentially enough kinetic energy from the impact, to not only pierce the steel case, but to trigger the primary explosive. If that primary explosive goes off, it's almost guaranteed to set of the secondary explosive, or main charge of the grenade.

Here's the thing, not all steels are equal at the best of times. It's get even more confusing when you just compare stainless steel to carbon steel. There's a lot to it. That while it's steel that is the outer body of a grenade, it doesn't mean if you're behind an inch of the same grade material at 300m you can laugh off heavy, repeated impacts.

Longer version, play Sniper Elite 3 on the harder difficulties or with full ballistics. Adjust for windage, lead, drop, learn to fire from good stances and my god, do everything you can to hide your shots. In addition to learning how to eye ball distance and windage, you can get an idea of what you can and can't shoot through. On top of that a very intimate and on some level worryingly understated view of just how bad bullets are for people. See the attached video.

https://www.youtube.com/watch?v=TZ90DP0XwC4

So apart from fuel tank explosions, it's about as close as many of us to it and I'm thankful for that fact.

adzling,
See my some of my posts on the matter. Sixty, seventy years, the basic idea behind the grenade hasn't changed that much in hundreds of years.
When in doubt, C4.

adzling

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« Reply #43 on: (15:04:16/07-15-14) »
hey lion!

yeah the idea of the grenade has not changed (much) but the explosives inside has.
and likely would continue to evolve as explosives have....

for example plastic explosives came about around ww2, which was about i dunno, 70 years ago?

the research i am seeing online all seems to be around how the explosives are binded/ modified to make them more stable/ provide more explosive force.

interesting stuff

considering they have made some significant break throughs in the past 5 years i would expect this to continue

but if you want to fix all R&D to currently available tech that's cool
it's your game ;-)

with all the wireless fancy PANs folks use you can get wireless triggered grenades that explode from a silent order of your brain, no vocalizations required.
and hey you can't do that today!


Reaver

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« Reply #44 on: (15:29:00/07-15-14) »
Care to work through that procedure?

The wireless signal does what exactly? (List it out, step by step from signal to detonation...)
Where am I going? And why am I in a hand basket ???

Remember: You can't fix Stupid. But you can beat on it with a 2x4 until it smartens up! Or dies.