The blast range a completely out of control


#22

Last time my friend said, while he driveing the car in the road, there’s chicken walker firing a grenade launcher at something on a far long distance, and yet, he still getting caught by fragments, the half of his HP loss and almost every clothes he wear, getting damage on a different levels,

and now, I can’t even guarantee throw a explosives without hurting myself, every explosives with the fragments has almost half chance backfire at me, things getting worst when you successful hack the tank drone, and the fragments hurt you most the time, and I test the blast range, make a remote grenade on 40 and 45 tiles, and it still hurt you! I can’t imagine what happen if grenade can hit you that far on real life.


#23

On current experimental (and on earlier 1 month old) I have not noticed any excessive lethal fragmentation damage. Sure there are some fragments flying by now and then, but it is to be expected.

IRL there are generally two types of anti-personel grenades - HE (offensive) and fragmentation (defensive). Most common defensive example is Soviet F1 grenade that trained soldier can throw up to 30-40m, it has effective neutralization range of 30m and shrapnel can fly up to 200m away (290 fragments traveling at 700m/s) so no, it can not be safely thrown unless you have cover to hind behind.

The main issue could be it’s confusing which explosive is HE and which is fragmentation type as it is not always clearly written in description if I recall correctly.


#24

Are the fragments still entering the vehicles though? The armor should be able to keep you safe in a vehicle like a tank or armored car.

Standard cars…maybe not. I know buckshot can get through at 10 feet(standard car door). But armored? Shouldn’t get the player chillin in a tank.


#25

Still getting my ass blast inside the armored vehicles, I guess it will need a huge programme to fix this problems, So mabye we just need to wait.


#26

I was playing and had gotten an SUV running. I saw a grenadier 3 overmap tiles away (edge of screen and really, just out of my monitors view) and popped him from inside the SUV. It seemed delayed a turn after the blast, but from this distance it ripped off a complete frame and quarterpanel section, and severely damaged several others but I barely lost a tick of health. (Not gonna debate the distance, although I wonder if we know just how far 1 tile is yet.) The SUV wasn’t armored. It does make me wonder if RNG was on my side or if it was a fluke.


#27

I’ve recently had landmines pepper damage all over the Sun Wave, and this all the way from the edge of the reality bubble, which seems way too far.


#28

ohh now the grenades has truly become realistic now? now i have reason to use grenades now.

what about grenades from grenade launcher?


#29

saw this on github (fragmentation armor fix above) and cures my boredom.


#31

Hmm my experince with such, differ from yours, as someone who also served, in DK, i never saw or heard of anyone dropping greandes on themself my whole time there.

But maybe the danish forces is just better at throwing :wink:


#32

Honestly i think we should implement a diveing mechanic then, where you go on the ground and take far less fragmentation damage if you do


#33

Fragmentation weapons simply shouldn’t have that kind of blast radius. The effective kill radius of a standard hand grenade is only several meters. The fragments are generally small, not particularly aerodynamic, and they aren’t accelerated nearly as efficiently as bullets.

In short, they suffer massive velocity falloff, and should pose little threat beyond 15m, and less against armored targets - and while fragments can in theory fall over 200m away, the reality is that anything flying even a meaningful fraction of that distance is following a higher ballistic trajectory and is going to be pose little more threat to people on the ground than random pieces of jagged pocket change tossed off a building.

Granted, a sufficiently large explosion or more specialized directional weapon such as a claymore will have better kill radius - but still nothing like even a handgun’s effective range unless the blast itself is so massive that the shockwave itself is a serious threat.


#34

That’s exactly the resource I used, AFAICT individuals within 5m of the grenade are expected to have a 95% mortality rate, and individuals within 15m are expected to have no more than a 50% mortality rate.
The lethality doesn’t drop to nothing at 16m, it falls off with roughly the inverse square of distance from the origin.
This reduction in lethality seems to be dominated by the cloud thinning out rather than drag induced deceleration while still relatively near the origin.


#35

The casualty radius is very different from the lethality radius that is described in the article - in military terms, a ‘casualty’ is any injury sufficient to have a soldier pulled from the battlefield, so a unit could suffer 50% casualties, and 0% mortality in a combat. If I roll out of my bunk and hit my head on the floor and concuss myself during a surprise attack, I’m a ‘casualty’. Maybe not getting a purple heart for that one tho…

Thus, the 15m casualty radius is the radius within which you’d be expected to suffer one or more injuries sufficient to potentially remove you from combat - very different from a lethal radius, especially given that our Survivor frequently is forced to fight through wounds which would be considered ‘casualties’ in warfare, as they don’t really have a rear line hospital to be carted off too (and they heal far faster than a real soldier, so the concept of a ‘casualty’ is very different in CDDA). Obviously you can still certainly be killed within that radius, with the equivalent of a ‘critical hit’ to a vulnerable spot such as an eye or vital organ, but generally speaking you’d just be suffering flesh wounds of a significantly lesser variety to those of small arms at the same range.

In terms of the physics, both the thinning of the particle cloud and the reduction in velocity are going to be relevant, though It’s much harder to calculate the latter without knowing specifics. The fragmented pieces will vary in size considerably and will thus vary in how fast they are moving initially and how quickly they slow down to terminal velocity. You’re more likely to be hit by smaller fragments, as they’ll be more numerous, but the injuries they cause will be lesser, and they’ll be more easily stopped by armor. The large fragments will be more dangerous AND will go further, but necessarily much fewer in number, so your odds of being hit by one outside of the first several meters is very low.

Under no circumstances should we expect any fragment from a standard grenade to have the velocity or momentum of, say, a standard .38 pistol round. The explosion is unconstrained and thus unable to efficiently accelerate the fragments. By the time the fragments are just a couple inches out from the initial center of the blast, the bulk of the explosive force will simply go around the fragments, quickly leaving them behind and failing to accelerate them much further. Most of the blast force is simply wasted, unless the target is close enough to suffer the direct effects of the shockwave, such as deafening and dazing - if they are close enough to suffer concussion and internal shock injuries from the blast wave itself, they’re probably inside that 95% lethality radius.

The reason that lethality drops off so incredibly fast for a grenade is that it is dropping off on several axes at once. The fragment cloud density is dropping with the square of the radius, the fragments are losing momentum at a drag coefficient far higher than that of a more massive, aerodynamic bullet, and all of them are suffering drop, which means that past a relatively short distance the velocity loss of fragments that can hit a target is even greater than the straight line distance indicates, because the only fragments reaching out past that first 15 meters or so must follow longer ballistic trajectories. This last matter may sound insignificant, but it is a large part of why many traps and bombs are set to air-burst, like bouncing betties. It allows a far larger proportion of the shockwaves and fragment cloud to engage targets at a ‘significant velocity’. Whereas a normal grenade going off on the ground is completely wasting at least 80% of its fragmentation volume, 40% being shot straight into the ground under it, ~40% being fired up into essentially harmless ballistic trajectories (as long as you aren’t standing on it when it goes off), and only a relatively thin ring around the edges moving on vectors that will directly threaten the intended victims. Air-bursting allows most of that lower 40% to come into play if a grenade goes off, between, say, 5-10 meters off the ground.

I think the big rule of thumb you should keep in mind is that in any kind of blast fragmentation, you should expect the fragments to AT BEST behave like a similar gauge of shot from a shotgun - in reality their scatter is far wider, and for any given fragment mass, their drag will be greater than the equivalent mass of shot. As far as initial velocity goes, it obviously depends on how much explosive was used, but generally speaking packing a lot more explosive behind the fragments has a very bad return on investment past a certain point (because most of the blast force is necessarily wasted due to the lack of a pressure containing mechanism such as the shotgun’s barrel), so realistically they just won’t be going that fast compared to a bullet from a gun or a bb from a shotgun.

Correction: I believe I was correct in saying that you see a bad return on investment for piling on more explosive past a certain point (in particular the point at which the blast factures the container) - however, the initial velocities of the fragments CAN be very high, because true explosives like TNT are much more energetic than standard gunpowder. So yes, your fragments might be going faster that bullets depending on details - but no, they won’t be doing so for long, as their drag coefficients are far higher than bullets.

Here’s a fascinating source on the subject, if a tad hard to read due to bad army copying machines. :smiley:


#36

Err sorry for the blather. I don’t care too much how grenades actually work in CDDA, I just find it fascinating to noodle on the detailed weapons physics. :smiley:

For example, it’s fascinating to note that the more aerodynamic your fragments are, the LESS efficiently they are accelerated by the initial blast shockwave - because the shockwave is allowed to flow around the fragments without imparting as much energy. Conversely, if they are flat planes, then they accelerate faster at the start, but then slow down quickly as well, making them more deadly close in, but reducing their maximum effective radius.

Bullets get a win/win in this scenario because of the constrained barrel, the flat back of the bullet and their aerodynamic nose shape - but shrapnel gets no such free lunch. The more aerodynamic your shrapnel is, the slower it comes out of the blast, and the less aerodynamic it is, the fast drag force yanks it back down to harmless velocity - and remember that drag is itself a squared formula, so the faster your shrapnel is to start, the faster it slows down, just like the density of fragments drops off with the square of the radius.

So in an extremely oversimplified form, you are looking at a lethality reduction of (Rd^2)*(Rv^2), where Rd fragment density, and Rv fragment velocity. THUS the incredibly high lethality within a few meters dropping down to a negligible lethality within 15m.


#37

You have a source for that? That sounds right but I’d like to get more detail about what qualifies if possible.
I can look into adjusting my tests to change what qualifies as a casualty, probably something like 40% hp loss.

Regarding initial velocity and velocity over time, theres a lot of good detail here https://www.researchgate.net/publication/235106871_The_Initial_Velocities_of_Fragments_from_Bombs_Shell_Grenades
In short, the velocity is reasonably modeled as the ratio of mass between explosive and casing, which is what I do internally. This results in very high velocities. They do drop off rapidly, but not as fast as you’re asserting.

For external ballistics I used this source
https://fas.org/man/dod-101/navy/docs/es310/warheads/Warheads.htm

I think the one thing I’m neglecting with grenades is the geometry of the blast, effectively ordinary grenades are acting like bounding mines. I’m not really clear how to factor that in.

You may or may not want to look at the code, I’m incorporating all of this:)


#38

Heh. You and I have clearly been reading similar papers.

So one thing I’ve been mistaken about is how initial velocity is calculated in a fragmentation weapon - the initial velocity appears to be dominated not by the pressure wave, but by the fragmentation stress of the canister. I knew that was a factor, but it appears to be the dominant factor in those equations, and it does suggest that initial velocities can be higher than I was musing.

Doesn’t change the drop off problem though. The faster an object is moving, the much greater its drag, and these fragments can be expected to have pretty lousy aerodynamics compared to bullets or even BBs. Any decent sized chunk is likely to be a tumbling irregular polygon, which should have an awful drag coefficient. The smaller bits can probably be treated more like spheres, but they have the problem of a bad mass/surface ratio, even if their drag coefficient is more favorable.

As for trajectories, a ground based blast is necessarily going to have ALL its effective fragments following shallow ballistic trajectories. The blast of a classical hand grenade is going off literally an inch or two off the ground, so anything following a flat trajectory is going to hit the dirt within a few yards, while anything firing off at more than a 30 angle is going to fly over the head of anyone beyond 4 meters - this leaves an increasingly narrow (vertical slice) cone of effective fragments as you step away from the epicenter. All those fragments launched on arcs above 30 degrees will have lost too much energy by the time they come back down to an altitude where they’d actually intersect anything to do serious damage.

In reality the devil is very much in the details. A grenade that rolls into a shallow divot will be far less deadly than one that manages to come to rest on a slight rise, simply due to the much more effective expression of its fragmentation radius. This is also why dropping prone or into shallow cover will very likely save your life from a nearby grenade. The ground itself combined with trajectory drop is creating a very narrow window for a fragment to find you in a prone position out past a few meters.

Alas, grenades roll downhill, so on uneven terrain they tend to lose a lot of effectiveness - unless of course your specific goal is to murder everyone inside said hole, such a a bunker or trench, in which case, go for it - that’s pretty much what grenades were designed for.

They aren’t really open field area denial weapons. For that you want air-burst artillery shells, bouncing betty mines, or a nice fixed machine gun.

I’m not sure any of this more detailed look matters very much in a functionally 2D world. Basically the chance of taking a hit drops off with the square of the distance, and the force of the hit if you DO take one is doing something fairly similar (though it’s using a different base distance value depending on the coefficient of drag, I think). Don’t really know which one is dominant but I’m pretty sure they’re both very important. Never heard of a jeep taking structural damage from a grenade that went off 50m away? :smiley:

EDIT: Whew, the rat-hole of ballistic coefficients vs. drag coefficients and the proper way to calculate them is deep. Not really an issue for something like CDDA where a reasonable approximation will more than suffice, but man, turns out this is a big deal for gun enthusiasts.


#39

In CDDA terms, grenades should be a pretty great weapon for survivors against zombies because they like to clump up, and they lack the survival instincts to drop prone or find cover from the impending blast AND they mostly don’t have the armor that would mitigate the lower energy impacts from fragments at longer ranges, which of course survivors do have from the mid game on.

Conversely, most survivors are substantially ‘harder’ targets than our standard soldier, as they tend to wear quite a lot more body armor, due to their propensity for getting up close and personal with the enemy, and for the most part they aren’t contending with firearms that would negate that armor (until the very late game, where you become reliant on super-heavy armor such as power armor, or on tricks to engage ranged enemies without facing retaliatory fire).

As such, I’d expect that the survivor is usually a much more survivable figure against a mid-to-long range grenade blast than the average soldier - though a point blank explosive blast is probably going to turn them into gibs save in the case of the aforementioned power armor.

This at least is what I’d expect to see in a relatively realistic game, based on the performance of a RL grenade vs modern lightly armored infantry - particularly our modern infantry armor is highly selective in its coverage, designed to heavily protect vital areas while entirely forgoing protection for limbs. Survivor’s armor is designed much more for complete coverage, which is particularly useful against arbitrarily random weapons such as grenades.


#40

I think you’re right about this, and I should be a little clearer - velocity doesn’t drop off that fast, but kinetic energy does, as it is v^2.

My guess is that your formulae are probably correct, but some of the base assumptions feeding into it may be off. If for example you are basing your lethality drop off on a ratio of 95% mortality at 5m and 50% mortality at 15m, vs a 95% mortality at 5m and a 50% casualty rate at 15m, it means that your BASE dropoff radius is probably far too generous. If you correct the inputs into your formulae such that the 15m radius results in a 50% chance of moderate injury, then you’ll probably be GTG.

Also bear in mind that most of these military documents appear to be assuming unarmored targets, not soldiers in full NABC armor or other such folderol. :smiley:

This is a pretty good breakdown of the definition of Casualty in military terms - it’s actually used VERY broadly, though in the case of a grenade casualty, I think we can confine our terms to ‘combat medical casualties’ as opposed to disease or desertion casualties. Though I suppose a comparatively sane soldier might still desert from service after a sufficiently close call with a high explosive. :wink:


#41

Where thiings also get confusing is if foreign explosive devices get into the mix. I know that a big thing with the Russian F1 grenade is that while the (translated) nomenclature uses the same terms, their meanings are different. What we would read as its lethality, in the US, would be as described above, but for the Soviet writing on the subject, they referred to as the range where injury (and thus death) may occur. This made the F1 grenade look like a handheld nuclear bomb until the definitions were fixed.

I’m no expert, but wouldn’t sufficiently large explosives also be able to cause considerable harm due to the concussive force alone?


#42

Yes, concussive force can cause direct injury. The most obvious one modelled in CDDA is temporary hearing loss.

IRL it can cause severe or permanent hearing loss, and as the concussive force increases it can cause actual concussions, and injuries due to compression and tearing, and it can propel you into other more solid objects (like the ground) hard enough to injure or kill you.

However, in the case of most military explosives, the concussive force is a good bit less of a concern than the fragments. The blast shock-wave loses power exceedingly quickly compared to the fragments, so it is generally only a concern very close to the blast - though in some restricted cases it can be more dangerous, as the shock-wave can propagate around corners whereas the fragmentation can’t generally do that.

Not sure how or if CDDA models blast shockwaves - most of this particular discussion has been about the physics of fragmentation.