Blast effects are too strong?

[Battlefront.com]

Pandur,

that made me exclude the "obvious", iam sorry for that. also didnt i said "...optical gear but can they look around corners downwards, also the coax cant be bend!?" wich implies for me that the coax cant lower that far.

Right, and I've asked Charles to look into that. The deflection of guns (up and down) is something specific for each vehicle and SHOULD be accurate. If the accurate numbers are in there then it appears there is a bug which is overriding the restriction.

whatever, i just want to make sure that i did not confuse my infantry getting coaxed in trench as too strong blast effects, you have to belive me that

No problem The reason I've pointed to your "mistake" is that this commonly happens when someone says "I think x thing in the game is wrong". Inevitably we have other people say "I feel that way too", but it turns out they really don't because the examples they are thinking of aren't really about that particular issue. It's important to strip those things out of the discussion otherwise it's impossible to get anywhere .

Adam1,

Interesting stuff there. What if any changes are going to be made to infantry squad behaviour in the next patch?

Too numerous to mention The standard 3x Fire Team Marines Rifle Squad highlighted shortcomings of the UI and certain TacAI behaviors that remain in v1.08, so many things were changed (and tweaked, then changed, then tweaked some more... etc.). Other things added as well.

Steve

[SlapHappy]

There are apparently two HE rounds used in the T-72. The older of the two is an all-TNT warhead. The other is RDX + TNT. Both warheads utilize 3.15 Kg of explosive....if this is of any value to the curious.

[SlapHappy]

Using a simple blast calculator I found online the T-72 warhead (6.94 pounds) can generate overpressure of about 6.25 PSI @ 24 feet (7.3 meters). This is enough to cause serious injury or death. This is even assuming an entirely TNT composition.

[Peach Operations]

Steve --

I'm pretty sure the gun elevation/depression in CMSF isn't working.. I had assumed in the past that it was just something you guys weren't going to simulate. Some screenshots from a test scenario, to illustrate:

Here's the Abrams in game shooting its coax too low:

Then there's the Abrams in game being told to shoot at an 8 story building's roof. Note that there's two explosions -- one from the propellant in the barrel (which is in the right place), and a second, on the sixth/seventh story (way above what the gun could shoot at). There were no other units shooting at the building at the moment. See the following image:

Also, the Bradley in this picture is being told to shoot at the roof of the same building. Note that the angle of the tracer isn't the same as the angle of the gun:

Same as above, but zoomed out a bit:

In the images involving the building, the vehicles shown should be about 8m from the building (if you look closely, you'll see that they're sitting on the boundary between a grass and dirt tile). I found that if you took the vehicle all the way up to the edge of the building, it won't shoot (which it shouldn't), but if you back it out one tile (ie, 8m) it does. Hope this helps.

[c3k]

Peach Operations,

Thanks. I, too, had thought that BF.C had purposely done this. I'd seen this behavior several times and shrugged it off. Thanks for documenting it.

Regards,

Ken

[SlapHappy]

Originally posted by SlapHappy:

Using a simple blast calculator I found online the T-72 warhead (6.94 pounds) can generate overpressure of about 6.25 PSI @ 24 feet (7.3 meters). This is enough to cause serious injury or death. This is even assuming an entirely TNT composition.

HHHMMMM...perhaps I was off-base

The human body can survive relatively high blast overpressure without experiencing

barotrauma. A 5 psi blast overpressure will rupture eardrums in about 1% of subjects,

and a 45 psi overpressure will cause eardrum rupture in about 99% of all subjects. The

threshold for lung damage occurs at about 15 psi blast overpressure. A 35-45 psi

overpressure may cause 1% fatalities, and 55 to 65 psi overpressure may cause 99%

fatalities. (Glasstone and Dolan, 1977; TM 5-1300, 1990)

Apparently 5+ PSI is enough to knock a building down on you...which kills you

[SlapHappy]

Doing some quick recalcs with the tool and using 55 PSI as the threshold of 99% kill rate, I determine that range from T-72 is 2.6 meters - very close to the kill zone of the 105mm shell Steve posted.

However, at the 24 foot range I posted earlier your only likely to be knocked on your ass with some short-term hearing damage. Unless a nice-sized chunk of shrapnel eviscerates you, of course

[Battlefront.com]

Peach Operations,

Thanks for the screenshots. I've sent the link to Charles to see what he thinks. I don't know when I'll hear back as he's doing some intensive programming right now.

SlapHappy,

Thanks for the data! Great stuff.

Yes, the amount of explosives, the type of shell, and the proportion of fragmentation mass are all simulated. This means a shell with low explosive and a lot of mass will have a fairly large shrapnel/debris damage radius proportional to its blast effect. Vice versa, a shell with a large amount of explosives and low shell mass has a proportionally higher blast effect relative to its shrapnel/debris effect.

In CMx1 this was not directly simulated, but it was approximated as best Charles could under the circumstances. One particular problem he used to have was balancing the Sherman's 75mm HE vs. the 76mm HE. The reason was they had very different balances, which meant different outcomes. However, the code wasn't set up to be that subtle. Now it is!

Steve

[Cpl Steiner]

Originally posted by Battlefront.com:

This means a shell with low explosive and a lot of mass will have a fairly large shrapnel/debris damage radius proportional to its blast effect. Vice versa, a shell with a large amount of explosives and low shell mass has a proportionally higher blast effect relative to its shrapnel/debris effect.

What, exactly, would this mean in game terms?

I'm guessing that a shell with a lot of explosives but low mass would have more chance of knocking a building down than one with high mass and less explosives.

What about casualties? Presumably terrorists add nails and the like to bombs because it increases the number of casualties, so an explosion with a high blast but low shrapnel content would presumably be less dangerous to personnel but more likely to knock a building down, which of course would be pretty dangerous to anyone inside.

I would also welcome an example of each type of shell from the game so I can see what the difference is for myself.

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[Battlefront.com]

Cpl Steiner,

I'm guessing that a shell with a lot of explosives but low mass would have more chance of knocking a building down than one with high mass and less explosives.

Correct. The thing that causes structural damage is, mostly, the blast effect and not the flinging of bits and pieces of stuff.

What about casualties? Presumably terrorists add nails and the like to bombs because it increases the number of casualties, so an explosion with a high blast but low shrapnel content would presumably be less dangerous to personnel but more likely to knock a building down, which of course would be pretty dangerous to anyone inside.

Correct. When you look at pictures of suicide bombers you'll notice that. If the suicide bomber is in a car loaded with explosives only, there is a lot of major damage in the immediate area to buildings, cars, and of course people. A suicide bomber with an explosives belt, loaded with ballbearings or nails, causes very little damage (proportional to the explosives, of course!) but may in fact kill and injure as many people. There are other reasons for this, obviously, but it's a simplified way to think about it.

I would also welcome an example of each type of shell from the game so I can see what the difference is for myself.

No such numbers exist, unfortunately. Unlike CMx1 where things were predetermined values, in CMx2 they are all physics. Charles has to actually run the code in a test environment to get numbers. Which is why I didn't post the 125mm values since he didn't have them handy The 105mm was handy because he recently revised the code and happened to have saved the results of that particular shell.

Here's are some rough rule of thumbs..

Basic properties

HE - frag more than blast

AP - blast more than frag

HEAT - significant blast and frag, sorta in balance

SABOT - very little blast and frag

Thermobaric - blast more than frag

Scope of effect

Size of round - the bigger the munition, the bigger the effects inherent for that type of round.

Terrain - open terrain tends to favor frag, closed tends to favor blast.

Impact - frag detonated in air increases lethality in natural terrain, likely decreases for structures/vehicles.

Target type - the harder the target, the more blast is important. The softer the target, the more frag is important.

Target density - the more spread out the target, the more frag is important. The more consolidated, the more blast is.

It's always been our philosophy that having a generalized sense of weapons and their effectiveness is far more important than having abstracted numbers staring you in the face. One can learn a lot more by observing the effects within the game than one can from staring at a spreadsheet layout of numbers. Grogs are welcome to disagree

Oh... and a footnote here. There is a huge diversity of shells out there so these generalized rules are good, but definitely not applicable to every situation. However, when you go to use something, or see it used against you, these generalized rules should hold up pretty good. If not, then you can make your own

Steve

[ June 24, 2008, 07:58 AM: Message edited by: Battlefront.com ]

[Battlefront.com]

SlapHappy... can you post the link to that website you're using, or at least email it to me? The 'ol Brain in Jar is curious about it

Steve

[Bigduke6]

Steve,

You may think I'm getting extreme. Me, I think we're getting a of a lot closer to understanding what's happening here. At least I am.

First I want to repeat some excellent data, and I have to say this is one of the reasons I hang around this forum, it is a terrific place to learn.

Ok, to start off we have Charles' numbers for the US 105mm HE shell.

Blast - lethal: 2.2m

Blast - casualty, might be killed: 4.5m

Blast - possible serious wound (i.e. casualty): 6.8m

Shrapnel - possibility of serious to light wounds (depending on distance): 144.6m

My Comment: Sounds ballpark right to me except shrapnel. I would say shrapnel certainly could hurt you at that distance, but the chances should be so low at that distance so as to be militarily insignificant.

Next, we have SlapHappy's outstanding research on overpressure and the 125mm HE round.

T-72 warhead (6.94 pounds) can generate overpressure of about 6.25 PSI @ 24 feet (7.3 meters).

However, at the 24 foot (edit: 7 meter) range I posted earlier your only likely to be knocked on your ass with some short-term hearing damage. Unless a nice-sized chunk of shrapnel eviscerates you, of course [smile]

Using 55 PSI as the threshold of 99% kill rate, I determine that range from T-72 is 2.6 meters - very close to the kill zone of the 105mm shell Steve posted.[b/]

A 5 psi blast overpressure will rupture eardrums in about 1% of subjects,

and a 45 psi overpressure will cause eardrum rupture in about 99% of all subjects. The

threshold for lung damage occurs at about 15 psi blast overpressure. A 35-45 psi

overpressure may cause 1% fatalities, and 55 to 65 psi overpressure may cause 99%

fatalities. (Glasstone and Dolan, 1977; TM 5-1300, 1990)

Next we have Steve's responses to my shameless needling, which I will reduce to short form for the sake of relative brevity:

1. CMSF does not replicate troopies flattening themselves and doing the emergency hide if a tank points its main gun their way.

2. CMSF necessarily packs troopies, sometimes, into a tigher area than they would cover in the real deal.

3. CMSF individual soldier spacing is better when the soldiers are moving, than when they are still.

4. CMSF does not replicate the roughly teardrop shape of main gun shell explosion, rather explosions are circular.

5. If a pixel soldier is really close to a big explosion, he is toast no matter what.

Finally we have the Russian government blurb on the 125mm HE shell dug up by me, wherin

effective frag vs. personnel area is given at 520 sq. m.

effective frag vs. personnel works out, given circular geometry, to a radius of 12.8 meters.

Steve of course said I needed to be more careful about introducing data to the discussion, as the Russian government boiler plate on the 125mm HE is, according to Steve, absurd.

Well, I can only respond: "Read the brochure carefully." The Russians say, in excellent English, and I quote The potent HE projectile ensures an anti-personnel fragmentation effect in an area of 520 sq.m effective fragmentation range unquote.

This is not a fan/hobbyist site either. This is Rusoboronservis, the Russian national arms manufacturer, talking about one of their bread and butter products.

Now maybe the boys at Rusoboronservis are lying, although I doubt that. Maybe they are low-balling, although somehow I doubt that too. Just maybe they're overselling - but even I think that's nuts.

I have no doubt, and trust me neither do they, that splinters from the shell can go a football field and further and kill somebody.

But the chances making that happen in a war consistently enough to have an effect aren't, apparently, high enough to make the threat effective. The Russians it seems to me are advertising the effective range, not the maximum theoretical lethal range.

Of course, effectiveness is relative, and I will lay 100 - 1 odds that what Russians consider a safe distance from an explosion, Americans consider unsafe.

Nonetheless, the fact remains, the Russian government appears to say the shell we are discussing, to wit the 125mm HE round, is, in the size of its area of effect, almost certainly smaller than it is modeled in CMSF.

So to recapitulate -

* Infantry vs. tanks is usually stationary and so clumped, and what's more important, clumped close to the lethal are of the burst.

* The HE burst is circular- not teardrop-shaped so the burst has a slightly or maybe even moderately better chance of covering the entire clump. But I think Steve is dead on, in most cases the area we are interested in is roughly circulate, in the "tail" of the teardrop the effects are moderate in any case.

* Tthe burst being circular is a bit more effective than a teardrop at encompassing a line of soldiers - a very common formation for infantry trying not to get shot by a tank, as the alternative is movement and getting cut down by the MGs, and a circle is wider than a teardrop, and so gets more of the line.

* THIS IS A GUESS, I MAY BE WRONG ON THIS. The lethal area of the shell is 2 - 3 meters but depth of trenches does not count, meaning a real soldier lying on the bottom of a real trench may be two or more meters below the lip of the trench where the shell explodes, but as far as CMSF is concerned, he is on the same level as and so right next to the shell.

In other words, it appears the only thing that counts when figuring distance from HE blast to infantry in a trench, is the x-axis distance from the point of detonation. There is no y-axis into a trench. Again, on this point I am speculating.

* The manufacturer of the 125mm shell gives an area of effectiveness substantially less, than the game gives it, although one must add the remark that effectiveness is relative.

To me, all that is enough to explain to me why CMSF squads usually get wiped out by single main gun HE rounds, even when the squads are prone in trenches, and further, that is enough lead me to believe that the death rate is not due to the inherent lethality of HE weapons modeled properly, but due to the simulation's improper modeling - in this case - of HE effects on infantry.

Please, let no one take this as an indictment of the CMSF system. In general, I think CMSF gets the job done fine. My focus here is narrow: tank HE vs. infantry, usually trying to avoid the HE any way it can. If any one objects to "improper modeling", please, by all means substitute "could be improved somewhat."

My recommendations take them or leave them would be:

- Increase the cover provided by trenches to prone infantry substantially, like, you have to hit a squad about 4-5 times on the nose with an HE shell to kill them in their trench. Now it is 1.

- Increase the chances of infantry going prone and if possible trying to hide, the moment a tank points its snout their way (this may not be possible) or if an HE shell goes off in the vicinity (this is certainly possible)

- Consider making infantry in trenches harder to hit on the nose, this is not quite accurate as shell accuracy is what it is, but as a practical matter this would represent infantry shuffling and hiding if they're targeted by a tank

- Bias infantry against standing up at all if a tank is in the vicinity, if the infantry can't harm the tank. In other words, introduce cowering behavior for infantry. Not sure this would fly from a "fun" perspective, but it would certainly be realistic.

- Reduce the effectiveness of HE at longer ranges (say, 20 - 60 meters) so that casualties are not

highly probable, but somewhat probable, and make casualty risk beyond that low to non-existent.

- Retain the "death at extreme close range" principle: if a pixel soldier is 3 meters or less from a 120mm+ blast he is dead or incapacitated somehow.

Finally, since Steve asked....

Think about it, though... do you really think a 125mm shell would only have a 12.8m maximum "reach out and touch someone" range?

In general, yes. That's about 3 kilos of explosive traveling at extremely high speed, blast dissipates fast, and I know courtesy of SlapHappy that the really dangerous overpressure from that round is a radius of about 3 meters max, and blast and severe frag risk out to something beyond that, and that frag and blast dissipates very quickly with distance. I know the explosion will be a teardrop not a circle.

I also know that Russian anti-personnel HE weaponry as a matter of principle depend first on blast to the expense of fragmentation, see the ISU series for precedent. What the Russians shoot for, if they have to choose, is overkill in a small area, not the risk of injury in a larger area; although of course the ideal is overkill in a large area.

So I put all that in my hopper and I answer yeah, if the Russians say anything in a teardrop maybe 6 - 18 meters around where their 125mm HE shell blows up is probably going to be hurt somehow, but beyond that and it's a crap shoot not worth anything to a tank crew wanting to shoot something with an HE shell, then that sounds more or less reasonable to me.

A M67 hand grenade has a total effective radius of 15m and a kill (Blast) radius of 5m. An RPG-7V's OG7V has a kill radius of 150m according to one source I just looked up. Are you saying that the 125mm HE round is less effective than a hand grenade? I am sure you aren't, therefore I ask that you kick the tires of your own argument a bit before posting

No, I am saying precisely that, and in passing you may rest assured very few of my arguements here are ever off the cuff.

As to the hand grenade, after all, a hand grenade was designed to throw little bits of metal at people and people only. It doesn't have to blow up buildings, crumble trenches, overpressure bunkers, smash equipment, or deal with soldiers in body armor. Nor does a hand grenade have to deal with travelling at a bazillion FPS to get to where it needs to be, to blow up. No teardrop burst for a handgrenade, it explodes nice and neat and circular. It flies at the speed of a softball, and since it arrives by lob it doesn't need the structural strength to travel down a main gun barrel at supersonic speeds on top of an explosive chage. Nope, all a hand grenade needs is enough resiliance to keep Joe from blowing himself up by accident, and all the rest of the weight can go to explosive for the fragments, and metal for the fragments, and even better the balance between can be almost perfectly efficient. All a hand grenade has to do is throw steel into flesh covered by cloth, no more, no less.

Now who was it that needed to kick argumental tires?

As to RPGs, well, an RPG-7 certainly will thow a splinter 150 meters that could kill if it hit a human, but so what? The key issue, at least for me, is effective range. How far away does a person have to be from the explosion, to have a reasonable chance of surviving? Where does the chance become unreasonable?

As a practical matter, I think you would agree with me that it would be a lot safer to be 10 meters away from an RPG-7 round detonating, than 10 meters away from a 125mm round detonating.

In any case, US hand grenades and RPG-7 rounds are superfluous here.

The issue as I see it is narrow: we have the generic 125mm HE round. We want to know, when it blows up where does its dangerous overpressure end? Where does the moderately dangerous overpressure end? Where does the dangerous frag risk end? Where does the moderate frag risk end; and of course, how accurately does CM2 replicate it? Especially when the target is infantry, and even more particularly when the infantry is in good cover?

[TheVulture]

Originally posted by Bigduke6:

Finally we have the Russian government blurb on the 125mm HE shell dug up by me, wherin

effective frag vs. personnel area is given at 520 sq. m.

effective frag vs. personnel works out, given circular geometry, to a radius of 12.8 meters.

Steve of course said I needed to be more careful about introducing data to the discussion, as the Russian government boiler plate on the 125mm HE is, according to Steve, absurd.

Well, I can only respond: "Read the brochure carefully." The Russians say, in excellent English, and I quote The potent HE projectile ensures an anti-personnel fragmentation effect in an area of 520 sq.m effective fragmentation range unquote.

This is not a fan/hobbyist site either. This is Rusoboronservis, the Russian national arms manufacturer, talking about one of their bread and butter products.

It's not entirely clear to me exactly what they mean. "The projectile... ensures an anti-personnel fragmentation effect in an area of..." could be talking about the area in which a person is virtually guaranteed to be hit by a significant piece shrapnel and disabled or killed. Which is essentially a measure of how many potentially lethal fragments are produced by a shell. 12.9m is the range inside of which there is a guaranteed casualty.

Of course, you can also read it to mean almost the exact opposite: outside the 520m^2 area (12.9m radius) there is no significant anti-personal effect at all. 12.9m is the range outside which you are completely safe.

And by extenstion, you could take it to mean anything in between - 12.9 m is the range at which the probability of a casualty falls below some significant limit.

Re the data Steve provided, the 144m distance from the 105mm shell sounds like it is talking about the range at which the density of fragments falls reaches some threshold below which (rather arbitrarily) chance of a casualty is negligible (it would presumably be a smooth function of distance with an arbitrary choice of when to stop caring about the risk). Plus presumably fragments slow over distance rendering them less lethal, although I have no idea what distance scales that would happen on for various sized pieces of shrapnel.

Incidentally, I notice that, fudging for the differences between 105mm and 125mm shell effects, the radii 12.9m and 144m are in a close to 10:1 ratio, so a bit of hand waving suggests that if you are looking at a highly likely kill at 12.9 m (say typically 1 fragment per person-sized space (assuming a person prone taking cover I'd guess)) then you are talking basically a 1% chance of being hit at 144m, which is as good a threshold as any to chose to stop caring about the probability of being hit in a simulation.

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[SlapHappy]

ATBlast

ATBlast is a software program that estimates the blast loads that develop during an open-air explosion. The program allows the user to input minimum and maximum range, explosive charge weight, and angle of incidence. From this information, ATBlast calculates the following values: Shock Front Velocity (V), Time of Arrival (TOA), Pressure (P), Impulse (I), and duration (td). The results are displayed on screen in a tabular format and may be printed. In addition, the resulting pressure and impulse curves may be displayed graphically. ATBlast is a proprietary computer program developed by Applied Research Associates Inc. and is provided at no cost to the government and to authorized users. To download the latest copy of ATBlast, click here.

http://www.protectiveglazing.org/resources/setupatblast.zip

[ June 24, 2008, 02:12 PM: Message edited by: SlapHappy ]

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[SlapHappy]

The blurb about human tolerances came from this PDF file about nuclear explosives effects:

http://198.246.98.21/niosh/docket/pdfs/NIOSH-125/125-Explosions%20and%20Refuge%20Chambers.pdf

Although, apparently, it was simply being cited from the source listed in the blurb. I've seen other examples that back up those tolerance figures, however.

[SlapHappy]

This seems to be the cadillac of explosives simulators:

http://www.blastfx.com/Software/ModelingWithBlastFX/tabid/59/Default.aspx

There are some screenshots of how the program works. If you run their example numbers through the ATBlast program, you will find the results match to exact figures. Too bad you have to be a firefighter or sumfink to even be allowed to purchase it. And I bet it's expensive, too.

[SlapHappy]

Here are the formulae for blast and fragmentation effects from generic warheads:

http://www.fas.org/man/dod-101/navy/docs/es310/warheads/Warheads.htm

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[SlapHappy]

Originally posted by Adam1:

I started working on a test scenario, but I can't get the bombs to drop. Anyone know what I did wrong?

Adam\

When I did my tests I used only one command squad (3 men) calling down various ordnances (artillery, air bombs, mortars) at various distances using target point command. I noticed when I tried using a small area fire command, the F-16 would always have "coming around" status and would fail to launch the bomb. It's also faster to set the artillery mission or bombing run before pressing the start button for the mission. This gives you results in under a minute, and if you want to speed things up it is generally quicker to just re-start the mission to make multiple tests.

[akd]

Although it concerns WWII, the following information might be useful to the discussion:

http://members.tripod.com/~nigelef/wt_of_fire.htm

This also brings up a question: does the type of terrain influence the explosive effects of an HE shell in CMSF?

The effects of terrain are many and varied and can markedly reduce the direct effects of bursting shells. In soft ground a shell will penetrate slightly deeper than in hard ground, this means that the crater will absorb more of the laterally projected fragments.

[ June 24, 2008, 02:48 PM: Message edited by: akd ]

[SlapHappy]

Originally posted by akd:

Although it concerns WWII, the following information might be useful to the discussion:

http://members.tripod.com/~nigelef/wt_of_fire.htm

Yah. I posted that one earlier in this thread...what's cool about that link is that it shows the typical "blast shape" of the ordnance based on the angle of impact. Also, it gives some indication of the effects of human posture on blast/shrapnel effects, which is another important part of the issue in the CMSF game.

[akd]

Originally posted by SlapHappy:

</font><blockquote>quote:</font><hr />Originally posted by akd:

Although it concerns WWII, the following information might be useful to the discussion:

http://members.tripod.com/~nigelef/wt_of_fire.htm

Yah. I posted that one earlier in this thread...what's cool about that link is that it shows the typical "blast shape" of the ordnance based on the angle of impact. Also, it gives some indication of the effects of human posture on blast/shrapnel effects, which is another important part of the issue in the CMSF game. </font>