Some random questions on stuff I've seen on tv.

[BTM]

Sometimes I watch movies and stuff, and I think, "Huh... could that REALLY happen?" or "Wait, why are they doing that?"  or even, "Does that work like that in real life?"

Sadly, most of these questions tend to revolve around weapons, weird situations, and crazy, even illegal activities.  So, where I could I ask them and not get a lot of crazy looks (or worse)? 

So, then I came up with the solution: HERE, on this board with all the other crazy people.  :)

Question 1:

Okay, ever seen those movies where you have bad guys (usually the mob) counterfeiting money?  One thing I see them do is take the newly printed bills and throw them into a clothes driver (sometimes with a bunch of poker chips.)  I believe they did that in Lethal Weapon 4, among other films. 

So, what's the deal with that?  I mean, is that to give the money a more realistic "used" look, so it isn't too brand new looking? 

Question 2:

If I were ever in a John Woo-like Mexican standoff (ie, me and bad guy standing just a few feet away, each with a gun pointed at the other person) wouldn't it all just be a matter oh who fires first?  Or could the second probably get off a shot even after the first just on pure trigger reflex?

Question 3:

Remember in the oriiginal Die Hard, there's a scene where John McClane is on a high floor and the terrorists down near the first are firing a rocket launcher at the SWAT tank?  John gets p**sed because Hans calls for another attack, so he grabs some plastic explosive (might have been C4, not sure), and starting plugging in detonators into it.  He plugs in two and says, "Ah, f**k it." and then plugs in the rest that he has on him.

Okay, I know plastique (sp?) needs an electrical charge to explode, but I'm assuming (correct me if I'm wrong) that hooking up extra detonators isn't going to add to the explosion, any more than say, lighting TWO fuses on a stick of dynamite.

Question 4:

Can water really slow down bullets enough that you wont' get killed?  You know, you see this a lot in films, guy good jumps into the water, bad guy(s) pull out guns, fire into the water, good guy isn't harmed.  I think they did a Mythbuster's ep about this, but I didn't see it.

And yes, I know the type gun of would probably make a difference in the experiment, but still.

Anyway, that's all I can think of for now. 

[Derf]

Sometimes I watch movies and stuff, and I think, "Huh... could that REALLY happen?" or "Wait, why are they doing that?"  or even, "Does that work like that in real life?"

[....]

Question 4:

Can water really slow down bullets enough that you wont' get killed?  You know, you see this a lot in films, guy good jumps into the water, bad guy(s) pull out guns, fire into the water, good guy isn't harmed.  I think they did a Mythbuster's ep about this, but I didn't see it.

And yes, I know the type gun of would probably make a difference in the experiment, but still.

Anyway, that's all I can think of for now. 

If I recall that episode correctly, they found that weapons that fired at a high velocity (faster out of the barrel) were most affected by water (i.e., you were safer underwater as the bullets didn't penetrate very far. With slower muzzle velocity, bullets penetrated deeper. So, if someone is firing a musket at you when you are in the water, you are possibly in trouble.

[CheezeFlixz]

Question 1 - Yes

Question 2 - Who fires first and who ducks second.

Question 3 -- C4 and the like need a concussion to detonate. If you was to roll C4 into a little ball and shot it with a sling shot it would explode upon contact. The detonators only provide the concussion blast to detonate it. The electrical is only needed for the detonators.

Question 4 - Water will also deflect bullets and alter it's trajectory in addition to slowing it down ... after all water is a tad more dense than air.

[ulthar]

Question 1 - Yes

Isn't there a little more to it than simply trying to make the money look 'less new'?  Real money has fiber threads 'woven' into the paper.  Some counterfeiters used to (it's not really all that effective) wash the money with old rags to 'embed' the paper with lint to reproduce this.

It's better to have the threads in the paper before it's printed.

Question 3 -- C4 and the like need a concussion to detonate. If you was to roll C4 into a little ball and shot it with a sling shot it would explode upon contact. The detonators only provide the concussion blast to detonate it. The electrical is only needed for the detonators.

Are you sure about that slingshot part?  There's a BIG difference between the shock generated by a cap (at least tens of kilobar moving at around 6000 meters per second) and a ball from a slingshot.

Pulling out my trusty copy of Mader's Numerical Modeling of Explosives and Propellants, in Chapter 4 we find a section titled "Projectile Initiation of Explosives."  The key parameter found in projectile initiation is V^2*d, where V is the velocity of the projectile and d is it's diameter.  If the V^2*d value for a projectile is smaller than the high explosives critial value, no detonation will occur.

I don't have numerical data for C4, but I do have for a 60-40 mix of RDX (the hi-ex component of C4) and TNT.  The critical value for this explosive is V^2*d = 5.8 mm^3/us^2.  This translates to 761 m/s for a 1 cm projectile hitting the surface of the explosive, or about 2200 fps.  For other hi-ex mixtures, such as Composition B3, the critical values are even higher.

You getting 2200 fps out of your slingshot?

Now, if you have eyeballs-on experience to the contrary, I'd love to hear about it - computational modeling of explosives, detonation initiation and the deflagration-detonation transfer is the kind of research that I do, so your observations would be relevant.

In practice, the real reason more than one detonator is used is reliability.  You also get some charge directionality from where the initiator is placed, so sometimes you can "focus" the blast a little bit with detonator placement.

[CheezeFlixz]

Question 1 - Yes

Isn't there a little more to it than simply trying to make the money look 'less new'?  Real money has fiber threads 'woven' into the paper.  Some counterfeiters used to (it's not really all that effective) wash the money with old rags to 'embed' the paper with lint to reproduce this.

It's better to have the threads in the paper before it's printed.

There is always an easier way, but at 1:25 AM it was the best answer you could get. I think the main reason for beating up the money is to distress it and to give it that used look. Getting your hands on REAL cotton fiber paper that money is printed on is nearly impossible. Only one company makes it, and only one government buys it and it's illegal to sale to anyone else.

Question 3 -- C4 and the like need a concussion to detonate. If you was to roll C4 into a little ball and shot it with a sling shot it would explode upon contact. The detonators only provide the concussion blast to detonate it. The electrical is only needed for the detonators.

Are you sure about that slingshot part?  There's a BIG difference between the shock generated by a cap (at least tens of kilobar moving at around 6000 meters per second) and a ball from a slingshot.

Pulling out my trusty copy of Mader's Numerical Modeling of Explosives and Propellants, in Chapter 4 we find a section titled "Projectile Initiation of Explosives."  The key parameter found in projectile initiation is V^2*d, where V is the velocity of the projectile and d is it's diameter.  If the V^2*d value for a projectile is smaller than the high explosives critial value, no detonation will occur.

I don't have numerical data for C4, but I do have for a 60-40 mix of RDX (the hi-ex component of C4) and TNT.  The critical value for this explosive is V^2*d = 5.8 mm^3/us^2.  This translates to 761 m/s for a 1 cm projectile hitting the surface of the explosive, or about 2200 fps.  For other hi-ex mixtures, such as Composition B3, the critical values are even higher.

You getting 2200 fps out of your slingshot?

Now, if you have eyeballs-on experience to the contrary, I'd love to hear about it - computational modeling of explosives, detonation initiation and the deflagration-detonation transfer is the kind of research that I do, so your observations would be relevant.

In practice, the real reason more than one detonator is used is reliability.  You also get some charge directionality from where the initiator is placed, so sometimes you can "focus" the blast a little bit with detonator placement.

Yes when I was in the military we use to take small balls of C4 and other same type of explosive and blow them up in this method for craps and giggles in Lebanon ... now disclaimer did it work every time? NO, only on occasion did it work. More often than not you'd just end up with a flattened dough ball of C4. It was not a controlled environment and using the same size ball hitting the same angle each time, about the only constant in was we'd fire them at concrete/brick walls from elevation down as not to get hit with debris on the occasion it did work.
This was in early 1980's (ca 82-85) so was the manufacturing process different then, was the chemical make up different then, was it old left over Viet Nam explosives, was it near the end of it's shelf life and unstable, I don't know. I was a 20's year old kid having fun, trying to stay alive in a dangerous place.
I can say, throwing it never worked, which we heard it would this prompting this "experiment". So figuring throwing wouldn't work we'd need a something faster, and being some 20+ years down the road was the success rate 1% or 50% I don't remember, but I'd say it would be closer to 1% or less.
Sometimes we had to much time on our hands while on watch.

[ulthar]

Okay...air bubbles or grit in the mix will drastically lower the critical value.  So I suppose especially if this was old stuff, 1% or so detonation success rate it is not undreasonable.  That it CAN work reads a little differently to me than it DOES work.

Cool.  I love experimental science.   

[Jack]

As far as bullets travelling through water, I saw that Mythbusters episode and if memory serves, a 9 mm handgun bullet would travel about nine feet through water and still be fairly deadly.  As they increased the velocity of the firearm, the bullets became less and less effective.  The friction of the water would tear the bullet apart before it travelled very far.  At the end they fired a 50 cal rifle into a swimming pool, and despite the enormous splash, the bullet didn't even hit a target three feet under water.  I think that was actually an armor piercing round, but I can't say for sure. 

[CheezeFlixz]

Okay...air bubbles or grit in the mix will drastically lower the critical value.  So I suppose especially if this was old stuff, 1% or so detonation success rate it is not undreasonable.  That it CAN work reads a little differently to me than it DOES work.

Cool.  I love experimental science.   

It is by luck only that I am still alive and for the more part unscarred. We'll make Napalm-like stuff from diesel and petroleum jelly. There is and I have somewhere a FMF (Fleet Marine Force) Manual that is nothing but how to make booby traps, bombs, and various other things. I do not know if it is still in government publication or not, I have boxes of old FMF and various other military manuals in storage. Maybe I'll see of I can find it one day. 

[ulthar]

There is and I have somewhere a FMF (Fleet Marine Force) Manual that is nothing but how to make booby traps, bombs, and various other things. I do not know if it is still in government publication or not, I have boxes of old FMF and various other military manuals in storage.

Dunno about the FMF manual, but the Army version of that is TM 31-210 "Improvised Munitions Handbook."  There's another one on incendiary devices, too, but I don't recall the TM number.

[CheezeFlixz]

Dunno about the FMF manual, but the Army version of that is TM 31-210 "Improvised Munitions Handbook."  There's another one on incendiary devices, too, but I don't recall the TM number.

That might be it or something like it, many Marine manuals were TM (Training Manual's) too, only branch specific manuals were tagged FMF or something like that, I haven't seen them in years. There was another called I think "Lessons Learned in Viet Nam" which also had dangerous ideas in them.

[zombie no.one]

the ghost of WyreWizard looms over this thread...

[BTM]

I have boxes of old FMF and various other military manuals in storage. Maybe I'll see of I can find it one day. 

You could probably make a killing off some of that stuff on eBay.  (Assuming of course, they'd let you sell it, they might be iffy on "making bombs" books.)

 

[BTM]

Yes when I was in the military we use to take small balls of C4 and other same type of explosive and blow them up in this method for craps and giggles in Lebanon

To quote the goblins from Warcraft Two, "Explosions are fun!"

[Killer Bees]

I have boxes of old FMF and various other military manuals in storage. Maybe I'll see of I can find it one day. 

You could probably make a killing off some of that stuff on eBay.  (Assuming of course, they'd let you sell it, they might be iffy on "making bombs" books.)

 

Doesn't your Constitution guarantee the right to free speech?  Aren't printing materials covered by that?

I could be wrong. I'm just going by what I've seen on Law and Order.   

[CheezeFlixz]

Doesn't your Constitution guarantee the right to free speech?  Aren't printing materials covered by that?

I could be wrong. I'm just going by what I've seen on Law and Order.   

Only the government can not restrict free speech, provided it falls within time place and manner. Meaning you yell "FIRE" in a crowded theater. BUT reseller, private companies can restrict speech and refuse to sale anything they want. Mainly if they think it will open them up to liabilities. i.e. you bought a bomb making book on ebay, you blew something up, the victim sues you and ebay. Doesn't mean they'll win, it's just the cost of the liability.