Breaching vs. Cutting, Arsenal Explosives question Options

[Faelan]

Or for instance in Arsenal we could use a shit load of ammonium nitrate based explosives to destroy heavily reinforced targets, where as in real life it won't crack a slab of steel reinforced concrete no matter how much explosive you pack on. The velocity of the actual explosion which is determined by the type of explosive, is the principal means of determining what type of explosive to use on particular materials.

I also agree on the detcord issue, great shit for cutting down trees (IMG:style_emoticons/default/smile.gif)

[Adarael]

...where as in real life it won't crack a slab of steel reinforced concrete no matter how much explosive you pack on.

The Oklahoma City Federal Building, many IFVs, Humvees, and other vehicles all beg to differ, yo. With enough Ammonium Nitrate, you can blow up just about anything. This is true of any explosive.

[kzt]

The Oklahoma City Federal Building, many IFVs, Humvees, and other vehicles all beg to differ, yo. With enough Ammonium Nitrate, you can blow up just about anything. This is true of any explosive.

That is simply wrong. What happened in OKC was that the charge destroyed or displaced columns G16, G20 and G24, resulting in the 3rd floor transfer girder failing, which brought down the floor slabs above it.

A light armored vehicle is a collection of parts bolted or welded together. If you use a large enough charge you can cause the joints to fail. If you use a sufficiently large charge you can toss the entire vehicle into the air and kill everyone inside. You will not actually produce a hole in the armor plate, though you might deform the vehicle structure such that you get blast wave entrance into the vehicle. For example, blowing in the windows. However, the use of ammonium nitrate in Iraq is unusual, as IEDs and factory produced mines are almost always filled with TNT or other high explosives that have a much higher detonation velocity.

[WearzManySkins]

Or for instance in Arsenal we could use a shit load of ammonium nitrate based explosives to destroy heavily reinforced targets, where as in real life it won't crack a slab of steel reinforced concrete no matter how much explosive you pack on. The velocity of the actual explosion which is determined by the type of explosive, is the principal means of determining what type of explosive to use on particular materials.

I also agree on the detcord issue, great shit for cutting down trees (IMG:style_emoticons/default/smile.gif)

Do not forget The Texas City Accident
Texas City Disaster

Many Steel Reinforced Concrete Structures were blown away in that one. Check your number/ facts. Get your noses out of the text books and get some RL experience.

kansas City

Ammonium Nitrate Explosion in Ryongchon Train Station

Chemical Plant Explosion

Cause of the Port Neal ammonium nitrate plant explosion

Explosion in a urea ammonium nitrate (UAN) fertiliser transfer pump

WMS

[WearzManySkins]

That is simply wrong. What happened in OKC was that the charge destroyed or displaced columns G16, G20 and G24, resulting in the 3rd floor transfer girder failing, which brought down the floor slabs above it.

A light armored vehicle is a collection of parts bolted or welded together. If you use a large enough change you can cause the joints to fail. If you use a sufficiently large change you can toss the entire vehicle into the air and kill everyone inside. You will not actually produce a hole in the armor plate, though you might deform the vehicle structure such that you get blast wave entrance into the vehicle. For exampel, blowing in the windows. However, the use of amonium nitrate in Iraq is unusual, as IEDs and factory produced mines are almost always filled with TNT or other high explosives that have a much higher detonation velocity.

Correct me if I am wrong but where not those columns made of reinforced concrete? (IMG:style_emoticons/default/devil.gif)

WMS

[Faelan]

Before you go telling me I am wrong please try to know something about what you are talking about. Most ammonium nitrate suicide bombers are using that as a basis for anti personnel damage, however they normally use a TNT booster for causing greater damage to structures and vehicles. RDX, PETN, HMX are preferred if available (principally RDX the other two are more specialized). The Oklahoma City bombing was surrounded by conjecture and conspiracy theory precisely because of the damage inflicted by what was supposedly a pure ammonium nitrate bomb. According to the court records traces of RDX was found at the OKC site. The conspiracy theories arose from assoreted government agencies attempting to cover up the fact that restricted high explosives had in fact been used. How they came to obtain it, and the weaknesses in the USA's regulation process were undoubtedly buried as part of national security (hello mr. terrorist dont bother smuggling it in you can just buy it here!) and a large measure of CYA. OKC was a huge embarrassment to the ATF precisely because they are responsible for keeping restricted explosives out of the hands of lunatics.

Lastly for your information I have done my fair share of demolition, and the explosive velocity vs. appropriate demolition targets is basically Demo 101.

KZT nice to see someone who has a clue.

WearzManySkins none of the articles you pointed out prove a thing. None of them have anything resembling actual composition of the targets. I can pretty much gurantee you most of the damage was from soil displacement and gravity. Also if you ever spent anytime overseas especially in what was the Communist Block (and yes North Korea uses similar construction techniques) you would realize that 90% of industrial and residential buildings are actually constructed of unreinforced cement block, which last time I checked is not real resistant to a sledgehammer much less any kind of explosive. Lastly my knowledge is text book and field.

[kzt]

Correct me if I am wrong but where not those columns made of reinforced concrete? (IMG:style_emoticons/default/devil.gif)

Yup. They failed in two ways, shear and brisance. In G20 the concrete was essentially blown apart as it was quite close to the truck (in the 10,000 PSI zone), the other two failed when overloaded, I think by the blast wave.

What happened under blast load on G20 is that the concrete is shattered and displaced, and the bent but uncut steel rebar collapses under the load of the rest of the building (as rebar isn't designed to be load bearing in compression). You can't cut reasonably thick steel with AnFo. You can bend it, you can shatter the backing and hence displace it, and you can fracture the joints, but it won't be directly penetrated by the blast itself.

[Kyoto Kid]

...this is where i miss the old complementary knowledge skill roll.

[WearzManySkins]

Not Anfo but the Port Chicago blast sheared off a concrete reinforced ammunition handling pier. The remains were visible for a long time.

Merely because you do not see any buildings of reinforced concrete does not mean any where not there. Records of buildings at those location may still be around.

WMS

[Faelan]

Probably because the Port Chicago blast was the result of mishandling of MILITARY MUNITIONS not ammonium nitrate.

[WearzManySkins]

Or for instance in Arsenal we could use a shit load of ammonium nitrate based explosives to destroy heavily reinforced targets, where as in real life it won't crack a slab of steel reinforced concrete no matter how much explosive you pack on. The velocity of the actual explosion which is determined by the type of explosive, is the principal means of determining what type of explosive to use on particular materials.

I also agree on the detcord issue, great shit for cutting down trees (IMG:style_emoticons/default/smile.gif)

OK your statement above emphasis mine, you stated that no amount of Anfo will crack a slap of concrete.

As what KZT has posted several the columns were "cracked" by the explosion, as for how the building was brought down is secondary. As to what exactly caused the "Cracking" is immaterial. Your statement above about not "cracking". You did not state blow a hole in it. If you had this discussion would have taken a different turn.

I did not talk of Terrorist explosions or events in contested war zone. I was proving your above state to be inaccurate at best.

Only one of the links I listed was in a Third Word Country, I will concede that NK has poor construction standards.

But in all of those listed explosions there were are reinforced concrete, the evidence by the blast is gone or been removed by reconstruction. But the piers in the Texas City and Port Chicago explosions were made of reinforced concrete, maybe not up to days standards but by the standards of then yes. Tell me how soil erosion took away those piers?

I am merely proving reinforced concrete can be "Cracked" by a explosion of Anfo.

WMS

[WearzManySkins]

Probably because the Port Chicago blast was the result of mishandling of MILITARY MUNITIONS not ammonium nitrate.

You miss my point, the Blast sheared off a reinforced concrete pier at the water line, I as also stated not Anfo.

WMS

[Faelan]

Misunderstood what Ampo was probably because it is not a term generally used to reference ammonium nitrate (unless you are looking for ANFO), which is what we were discussing. We were discussing ammonium nitrate so the fact that military munitions (of which very few are ammonium nitraete based) caused that kind of damage is not surprising.

Additionally when I said crack more accurately I should have said shatter, or break. The brisance of ammonium nitrate is insufficent in itself to crack or break or shatter steel reinforced concrete. Damage can still occur due to other factors of the explosion, such as what is the target resting on, what are supporting structures made of and how are they supported. Is the reinforcement continuous or not. If I have enough explosive to level everything in a 500m radius a lot of the damage will result from the shockwave both in the air and through the ground displacing supporting material (earth or unreinforced materials) or by applying force in a direction from which the materials are not reinforced resulting in displacement, at which point gravity takes over inflicting the actual damage. The end damage is not what I was referring to.

[WearzManySkins]

(IMG:style_emoticons/default/rotfl.gif) "Look Seaman Recruit Nelson is the light on or off, pike your electron flow lectures techno babble."

WMS

[kzt]

Typical concrete is about 3000 PSI strength in compression, good concrete up to 5000 PSI. At 10,000 PSI pressure the concrete internally fails, irrespective of what produces the pressure. The steel rebar will not be broken by this, but most of the compressive strength in a reinforced concrete structure is from the concrete. You apparently get similar effects with using HE or small arms to mouse hole breach a reinforced concrete wall, in that you blow a hole in the concrete but the hole is still blocked by the rebar. Then you have to cut the rebar in some fashion to get in.

[DeadLogic]

As soon as I read about square roots, I decided to house rule this nonsense. I thought I left this kind of math behind in SR3, nyuh. (IMG:style_emoticons/default/wink.gif) Anyone have an simplified houserules for this stuff? OR, we could come up with a chart? I dunno, but my runs are fast paced enough that if my runners are stopping to calculate square roots and stuff, they'll most likely get cacked... and I'd like to see an "action-movie" sequence every once in a while where they can just plant an explosive and have it go off. But you know, that's just how I roll. (IMG:style_emoticons/default/spin.gif)

[Dumori]

Yes a table for explosives would be a nice idea but could be a lot of work think about the variables.

[TheOneRonin]

As soon as I read about square roots, I decided to house rule this nonsense. I thought I left this kind of math behind in SR3, nyuh. (IMG:style_emoticons/default/wink.gif) Anyone have an simplified houserules for this stuff? OR, we could come up with a chart? I dunno, but my runs are fast paced enough that if my runners are stopping to calculate square roots and stuff, they'll most likely get cacked... and I'd like to see an "action-movie" sequence every once in a while where they can just plant an explosive and have it go off. But you know, that's just how I roll. (IMG:style_emoticons/default/spin.gif)

Well, first off, if the runners are in a hurry, I seriously doubt they would stop to make a calculation on how many kilos they need, exactly, to breach a wall/door/whatever. The smart ones will have this all figured out ahead of time, and will have the chart pulled up on their commlink/image link. Either that, or they bring along more than enough explosives to make their exit, and just don't worry about the exact quantity needed to do the job. The only time I can see a runner sitting down with a calculator and doing the math is when time isn't a factor, and this can happen quite often.

As for a quick chart, Arsenal has just that...but I'm not sure if posting it would be against copyright laws or not. Honestly, if you have some time, a calculator, and index cards, you can make your own chart and just have it handy for when you are playing.

Personally, I've created a spreadsheet in excel that does all the calculations for me.

Edit: Square roots aren't terribly hard to figure out, especially if you have a calculator. Look earlier in this thread...the formulas are realtively simple.

[Faelan]

Mind sharing that excel sheet with the rest of us (IMG:style_emoticons/default/smile.gif)

[TheOneRonin]

Sure. Gimme a place to host it and I'll put it up for all to see/use.

[WearzManySkins]

I too used a spreadsheet for use with the old "Demolitions" skill, all I have to do input the armor value, value of the explosive, and numbers of successes, then it gave me the amount of explosives to put a 1 meter hole, 2 meter hole and to totally destroy the barrier.

But since the Arsenal rules have come into light, I have not yet modified the sheet.

WMS

[kzt]

One of the marks of someone who knows what they are doing is they don't stop to look stuff up for trivial issues, and know when and how to methodically solve complex issues. A skilled explosives expert will have some rules of thumb that will get stuff done when speed is more important than finesse or cost. If he's doing complex work that requires precise effects or minimal explosives on hand he's probably going to start crunching numbers.

Also guys who have demo 1 and don't spend 10 minutes setting up the charge in a very methodical, checklist fashion tend to not be around long enough to learn demo 2.

[Faelan]

Especially when they like to wear wool and play with electric blasting caps.

[kigmatzomat]

Typical concrete is about 3000 PSI strength in compression, good concrete up to 5000 PSI. At 10,000 PSI pressure the concrete internally fails, irrespective of what produces the pressure. The steel rebar will not be broken by this, but most of the compressive strength in a reinforced concrete structure is from the concrete. You apparently get similar effects with using HE or small arms to mouse hole breach a reinforced concrete wall, in that you blow a hole in the concrete but the hole is still blocked by the rebar. Then you have to cut the rebar in some fashion to get in.

Some of the variance is between contained and uncontained blasts. If you put a big barrel of ANFO on a concrete slab in an open field the pressure wave will follow the path of least resistance and leave the concrete fairly unscathed. Put the same ANFO in a van under an overhanging building and you've added constraints to the blast that do much more horrible things.

Of course, high energy/short duration events, like explosions, tend to have their own rules. Explosives can be used to weld, bend, cut, and demolish all kinds of things in counter-intuitive fashions.

Getting back on topic, I'd say simplify the mechanics. A lot. My quick'n dirty suggestion would be to reduce the size of the effective hole by the demolition (cutting charge) Test (Threshold 1). E.g. MadBomberWhatBombsAtMidnight (MBWBAM) gets wants a 7 meter diameter hole. He gets four successes on his demo skill. (4 successes -1 threshold = 3 net) MBWBAM now calculates the explosives needed as if he were making a (7-3net successes =4) meter hole. The counter is that it takes ~1 minute/kilo of explosives as you shape/sculpt them into the right configuration.

[TheOneRonin]

Getting back on topic, I'd say simplify the mechanics. A lot. My quick'n dirty suggestion would be to reduce the size of the effective hole by the demolition (cutting charge) Test (Threshold 1). E.g. MadBomberWhatBombsAtMidnight (MBWBAM) gets wants a 7 meter diameter hole. He gets four successes on his demo skill. (4 successes -1 threshold = 3 net) MBWBAM now calculates the explosives needed as if he were making a (7-3net successes =4) meter hole. The counter is that it takes ~1 minute/kilo of explosives as you shape/sculpt them into the right configuration.

Okay, lets see how this pans out.

First, let's assume Rating 6 Foam explosive, since that's the max rating you can get at chargen.


BREACHING

We start with a Reinforced Wall (Armor: 8 / Structure: 9)

We use the base rules for breaching, assuming we are able to spray the foam explosive on the wall, 3.5 meters up (if we want a 7 meter diameter hole)

DV required = (Radius[m] x Structure Rating) + (Armor Rating ÷ 4)
Explosive weight = (DV ÷ DV Multiplier ÷ Explosives Rating)squared in kg


DV required = (3.5 x 9) + (8 / 4)
DV required = 31.5 + 2
DV required = 34 (rounded up from 33.5)

Explosive weight = (34 ÷ 2 ÷ 6) squared in kilos
Explosive weight = (2.83) squared in kilos
Explosive weight = 8.027 kilos

So if we are simply breaching, we can get that 7m diameter hole with 8 kilos of rating 6 foam explosive.


Cutting the same hole should take a much smaller quantity of explosives, so lets see how your suggested rule works:


CUTTING

Assume we make 4 net hits on our Demolitions (Threshold 1) test. That gives us 3 net hits (just like your example)

Just like your example, he uses the breaching rules, but assumes a 4m diameter hole instead of a 7m diameter hole.

I'm also going to assume we use the same x2 multiplier that we did for the breaching calculation

DV required = (Radius[m] x Structure Rating) + (Armor Rating ÷ 4)
Explosive weight = (DV ÷ DV Multiplier ÷ Explosives Rating)squared in kg

DV required = (2 x 9) + (8 ÷ 4)
DV required = (18) + (2)
DV required = 20

Explosive weight = (20 ÷ 2 ÷ 6) squared in kilos
Explosive weight = (1.6666) squared in kilos
Explosive weight = 2.7777 kilos


Not bad. As long as we use the same multiplier, cutting almost 3 times as efficient as breaching.

However, that ratio changes A LOT if your breaching charge is above the ground AND tamped (only 3.56kilos needed).

And Breaching actually gets BETTER than Cutting if you can put your explosives inside the wall, or underwater and deeper than the radius of the hole (2 kilos needed).

And how would you handle something like the linear cutting charges in Arsenal? Or what if you need a square hole cut instead of a round one?