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Guidelines for Surface Explosions

Antoniofer

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Ok, I planned to do this some time ago... like 3 years ago, but at that time I was finishing university and should have forgoten about it or simply lost the interest, but now that i'm "free" (I'm not running the risk of failing a class at least), I can make a thread about it.

Currently with have the Explosion Radius/Area page as reference how much an explosion yields in relation to its radius, but that only covers airburst explosion (or what is the same, thos ethat explode in mid-air, most common with nuclear explosion), but we do not have a reference page that expand into ground-level explosion. As a result, I made a blog 3 years ago: Surface Explosions: Effects and Radius. It haven't been altered in over 3 years, but I believe our standards for explosions haven't changed, although I would reccommend giving it a look.

The blog does not only give a yield/radius relationship for 20 psi explosions, but also gives yoy the different equations for different values of pressure the shockwave possesses (named overpressure), with the respective destructive reference to how determinate what overpressure should have an explosion. This is important since I noticed that several explosions calcs uses the 20 psi equation when there's nothing taht suggests the overpressure is that high.

So this thread is to add the Surface Explosion tables to the guidelines, doing the necessary adjustments.
 

Armorchompy

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Just so I understand, what value would you say a "baseline" explosion is? Like, an explosion that we don't see the result of, but we have no reason to assume is particularly weak. Because while I do agree in differentiating explosions based on pressure, using the 0.15 PSI end for a generic explosion would probably be less accurate than what we do not.
 

Armorchompy

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Also, I might be misunderstanding something but those equations might have a typo in them, ambiguous syntax or something because the results don't scale upwards as they should- the way they're phrased a 4 PSI explosion is stronger than a 9 PSI one.
 

Antoniofer

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Is difficult to rate an explosion that didin't cause any notable change in the environment, as there's no point of reference, so I would say there's no "baseline" assumption for an explosion. Calculationg an explosion based on its fire radius could be possible, but we do not have a equation that relate fireball to radius for surface explosions, additionally, when a "explosion" is just a bunch of fire that carries next to no pressure (or not pressure at all), then one does not use the explosion equation, as it is more of a combustion than anything.

As for the 4 psi thinky, rupture is more in the sense of bending crushing metal rather than tearing it, and according to this document, pressures of 34 kPa (~5 psi) is needed to cause severe damage to cars.

Mmm, I noticed now that at least one link can't be accessed anymore.
 

Armorchompy

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Is difficult to rate an explosion that didin't cause any notable change in the environment, as there's no point of reference, so I would say there's no "baseline" assumption for an explosion. Calculationg an explosion based on its fire radius could be possible, but we do not have a equation that relate fireball to radius for surface explosions, additionally, when a "explosion" is just a bunch of fire that carries next to no pressure (or not pressure at all), then one does not use the explosion equation, as it is more of a combustion than anything.
I dunno then, there's a lot of feats that are just big explosions/shockwaves that don't have any clear strength, completely invalidating them is iffy IMO.
As for the 4 psi thinky, rupture is more in the sense of bending crushing metal rather than tearing it, and according to this document, pressures of 34 kPa (~5 psi) is needed to cause severe damage to cars.
No, I mean the formulas, for example:
20^3*6.058^(-6) = 0.1618 Tons
20^3*11.8238^(-6) = 0.0029 Tons
I assume this is because of some math syntax ambiguity?
 

Antoniofer

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I dunno then, there's a lot of feats that are just big explosions/shockwaves that don't have any clear strength, completely invalidating them is iffy IMO.
Can't say they those explosions yield nothing, but if there's a ezolosion that cover certain area and withing tat area there is furniture and walls that suffered damage not according to overpressures above 20 psi (or not damage at all), than we couldn't assume that at the fartest point of the explosion is where the 20 psi shockwave reached.
 

Armorchompy

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I mean, maybe, but we still need some way to estimate, like, a 9-B explosion that happens on a barren field.
 

Antoniofer

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Mmm, we can't neither assume that the maximum range of an explosion is 20 psi, an explosion does not suddely stop at that point, and is not like pressures below 20 psi are harmless, for instance 9 psi op can also be pretty destructive, and so are 6 psi. I believe we would need to discuss that here.
 

DemonGodMitchAubin

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I mean this seems fine I guess, we usually assume 20 PSI in general

Most explosions I've calced involve completely destroying everything that's within the radius, so I don't know about explosions that exist in a vacuum
 

Antvasima

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Just a note that you can mention to me if you ever want your old staff position back Antoniofer. Staff members now also get all advertisements in this forum automatically removed.
 

DemonGodMitchAubin

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See I really don't know what to say about explosions that do not notably destroy anything nearby, since like I've said most explosion feats I've ever calculated are huge explosions that obliterate buildings, concrete, the ground, and everything else, basically nuking everything within the radius

So yeah... Not sure about other stuff
 
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See I really don't know what to say about explosions that do not notably destroy anything nearby, since like I've said most explosion feats I've ever calculated are huge explosions that obliterate buildings, concrete, the ground, and everything else, basically nuking everything within the radius

So yeah... Not sure about other stuff
Other stuff is prolly based on a case-by-case basis depending on what stuff we see destroyed.

I do remember there being requirements for higher overpressures to kill humans by destroying their organs with shockwaves, 500 psi IIRC. But IDK.
 

Antoniofer

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Most explosions I've calced involve completely destroying everything that's within the radius, so I don't know about explosions that exist in a vacuum
Not all explosions involve completely annihilating everything within the AoE, some of them do not cause as much damage, I'm refering to explosions that suddely stop one they impact with certain obstacle (generally a wall).
 

Armorchompy

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Also, these revisions don't impact air blasts at all, right? Is it simply us being unable to account for pressure in those explosions?
 

DemonGodMitchAubin

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Not all explosions involve completely annihilating everything within the AoE, some of them do not cause as much damage, I'm refering to explosions that suddely stop one they impact with certain obstacle (generally a wall).
Hmmmm, so like Bakugo?
 

Antoniofer

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For example, if there's an explosion of 20 m radius, and within that area there's a concrete pillar; if after the explosion the pillar remain with little damage or even unharmed, is logical to think that, from the origin of the explosion to the point where the pillar was located, the explosuin didn't reach a 20 psi OP, otherwise it would have destroyed the pillar.
 

KieranH10

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I agree with this. Having different over pressure values would be incredibly helpful.

Just to be sure. Would this be applicable to explosions that are more in-line with shockwaves? As these generally reach these pressure levels and have similar effects to the lower levels iirc.
 

DemonGodMitchAubin

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For example, if there's an explosion of 20 m radius, and within that area there's a concrete pillar; if after the explosion the pillar remain with little damage or even unharmed, is logical to think that, from the origin of the explosion to the point where the pillar was located, the explosuin didn't reach a 20 psi OP, otherwise it would have destroyed the pillar.
What about something like this?
Bz1CTkk.jpg

Or this
4y97XtU.png
 

TheRustyOne

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He's destroyed part of a building, but yeah Bakugo's explosions take place between buildings and while they cause damage. They don't destroy the buildings that are right next to them.

However does this include explosions that use the air burst formula as well?
 

Antoniofer

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@DemonGodMitchAubin, although I would not consider spherical aoe attack as explosions, for simplicity they are considered 20 psi since they tend to annihilate everything within the ao. I'm not quite sure what I'm seeing in tye second picture.
 

Antoniofer

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However does this include explosions that use the air burst formula as well?
In theory, yes, however, I've never seen the airburst explosion formula where the overpressure is kown (our current formula already incorporates the 20 psi).
 

TheRustyOne

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I've been curious about this, but would Re-Destro's feat be alright or not? I guess this is a question for every single physical shockwave produce.

He creates a shockwave with his attack that is strong enough to destroy multiple city block. The buildings we see here are very much destroyed, but would this not count since it isn't a detonation? Are 20 PSI for things like this no good?

And this is the air burst I was thinking about, is using the formula incorrect there?
 

Antoniofer

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He creates a shockwave with his attack that is strong enough to destroy multiple city block. The buildings we see here are very much destroyed, but would this not count since it isn't a detonation? Are 20 PSI for things like this no good?
I recall that the 40-50% of the energy of a detonation involve heat (actually, I write that in the blog), in which case if there's a shockwave that does not involve a heat element one can use the conventional equation and then multiply the result by 0.4-0.5; however, I could confuse that with the nuclear energy from airburst, so I may be wrong.
And this is the air burst I was thinking about, is using the formula incorrect there?
I understand that Bakugo turns his sweat in nitroglicerine and shoots the explosion from his hand, isn't it? I'm tempted to say it shouldn't use the surface equation sisnce the explosion doe not make contact with the ground (since the pressure of a surface explosions "bounces" with the ground in alters the real radius of the explosions, reason why surface-level explosions tend to have lower range that does that are air-level), but maybe the distance beween the hand and the ground could be considered negligible and could be considered surface area. In any case, if Bakugo shoots to the air then the air-burst equation should be more appropiated.
 
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I recall that the 40-50% of the energy of a detonation involve heat (actually, I write that in the blog), in which case if there's a shockwave that does not involve a heat element one can use the conventional equation and then multiply the result by 0.4-0.5; however, I could confuse that with the nuclear energy from airburst, so I may be wrong.
That is indeed nuclear energy from air-burst, yes. Though it's only for actual nukes.
 

TheRustyOne

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I did use airburst for that explosion, as seen here. (His sweat is stated to be like nitroglycerine, not 100% nitroglycerine)

For Re-Destro I was ask the same thing and was told the 50% energy thing comes from nuclear energy airburst. However DT did say this a very long time ago.

"No idea. The formula was never my area of expertise. Since it's based on TNT explosions, IIRC, I assume there is some energy not contributing to the shockwave, but I have no idea how much.

I won't hang you for leaving the full value. Ideally we would somehow figure out if there is much influence, though."


Basically we don't know how much energy comes from the shockwave vs the heat. Though maybe it'd be best to ask DT again, or to see if anyone found any information regarding it this.
 

Antoniofer

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That is indeed nuclear energy from air-burst, yes. Though it's only for actual nukes.
I thought so, then we do not have a relationship between overpressure and heat of an explosion.
I'm kind of in the same boat as Mitch here, as most explosions I've done have been ones that completely destroy the surrounding area.
I do not have problems with AoE blasts that completely destroy everything within the area, the equation is more when destruction within the area does not fit more with what an op of 20 psi would cause. For example, there's an explosion inside a wooden shack, and the detonation was unable to destroy the walls of the shack, then at the distance between the origin point and the walls the explosion couldn't have more OP than 6 psi (that according to the table, is the point at wich wooden buildings are destroyed).
 

Migue79

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The OP checks out.

I've seen explosions/shockwaves that don't affect the surroundings all that much, so this is a step in the right direction to deal with them.
 

Jasonsith

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I do not know if my question is appropriate:

1. How does an explosion that creates a large mushroom cloud that does little to unknown damage to surroundings count and what calculation will be adopted? Like...


2. (Maybe off topic) how does that change for Earth surface curvature? I am working on one calculation (possible redux) that may involve such and I think I have a model for that.
 

Antoniofer

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1. How does an explosion that creates a large mushroom cloud that does little to unknown damage to surroundings count and what calculation will be adopted? Like...
I would say that the effect of the explosion takes priority over the aesthetic, so even if it produces a gargantuan mushroom cloud but the surroundings didn't took damage relative to the coud's size, then you calculate based in the environmental effects and disregard the cloud.

I couldn't respond that second question, is nit my area of expertise.
 
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2. (Maybe off topic) how does that change for Earth surface curvature? I am working on one calculation (possible redux) that may involve such and I think I have a model for that.
Not exactly sure how the earth's curvature would change the yield of the explosion tho. It'd be just basic pixel-scaling at that point using the new curvature formula we've been using since last year.
 

DontTalkDT

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Adding pre-computed values from the existing formulas seem uncontroversial.

The 20psi revision you suggest on the other hand is probably more controversial. I mean, usually we measure not the shockwave since comics and stuff often don't really show it. We usually scale the area inside the fireball or what you want to call it for energy beam explosions and then go with the reasoning that inside this area every human would certainly have died and hence the "near-total fatalities"-value applies (which is 20 psi).
If you have an explosion where you scale the shockwave and a human might actually survive in that distance, I guess using the other values makes sense.
 

Antoniofer

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So I believe you suggests that for explosions with no real point of reference (like causing destruction or causing death) we consider the fireball as the 20 psi point, isn't it? Isn't the fireball radius considerable different than the 20 psi one according to online calculators?

Guess you agree with explosions that do not fit the destructive criteria at certain distance to use a different overpressure value, even if there's no proof that the explosions would or not kill every human within the radius, right?
 

DemonGodMitchAubin

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Adding pre-computed values from the existing formulas seem uncontroversial.

The 20psi revision you suggest on the other hand is probably more controversial. I mean, usually we measure not the shockwave since comics and stuff often don't really show it. We usually scale the area inside the fireball or what you want to call it for energy beam explosions and then go with the reasoning that inside this area every human would certainly have died and hence the "near-total fatalities"-value applies (which is 20 psi).
If you have an explosion where you scale the shockwave and a human might actually survive in that distance, I guess using the other values makes sense.
That’s true, it is usually implied that anything within the fireball itself gets destroyed, but in cases where it doesn’t, I guess that should use a different PSI?
 

Armorchompy

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What if we just use airblast for that? Even if it's a ground blast, it should still be more accurate since that formula doesn't use PSI, so it's better then guessing. Maybe. Idk
 

Antoniofer

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The airburst equation does use overpressure, but is already considered into the equation (20 psi); the more simplified equation for airburst is yet unknown.
 

DontTalkDT

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So I believe you suggests that for explosions with no real point of reference (like causing destruction or causing death) we consider the fireball as the 20 psi point, isn't it? Isn't the fireball radius considerable different than the 20 psi one according to online calculators?
The 20psi radius is usually much larger, so it would at least be a low end, I think.

But it often is less about the fireball itself than about the fact that we can be fairly certain that a normal human would have died in that radius.

Guess you agree with explosions that do not fit the destructive criteria at certain distance to use a different overpressure value, even if there's no proof that the explosions would or not kill every human within the radius, right?
If we can't assume that near-total fatalities apply for some reason, then another psi value fitting the destruction should be used.
As often in fiction, whether near-total fatalities should be assumed is a pro vs con issue. If there is a lack of destruction where destruction should be that's a big con. But there could be pro's to consider to counter that.
 

Antoniofer

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Hm, would need to check a calculator to confirm that, although my pc is ruined and my attemp of laptop do not leave me enter few sites. If that relationship between fireball and explosion is true then I guess I would have no problem assuming such a thing, although its imortant to notice that not all fireballs are explosions, thos ethat carries almost no pressure are combustions and should use other equation to determinate the yield.
 

Jasonsith

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Adding pre-computed values from the existing formulas seem uncontroversial.

The 20psi revision you suggest on the other hand is probably more controversial. I mean, usually we measure not the shockwave since comics and stuff often don't really show it. We usually scale the area inside the fireball or what you want to call it for energy beam explosions and then go with the reasoning that inside this area every human would certainly have died and hence the "near-total fatalities"-value applies (which is 20 psi).
If you have an explosion where you scale the shockwave and a human might actually survive in that distance, I guess using the other values makes sense.
Back to the 20 psi thing:

I do not know if it is any good, but a 20 psi overpressure actually represents a "heavy blast damage radius" or "near-total fatality radius" while a true "fireball radius" is effectively "liquifying/pulverising/vaporising radius" and is significantly a much smaller radius. While a 5 psi can still make up for a "moderate blast damage radius" and buildings can still be fragmented and organisms hurt or killed, and a 1 psi radius or the so-called At around 1 psi, glass windows can still be expected to break but is already but an explosion with a certain yield, if having a certain "heavy blast damage radius", will have a much larger "light blast damage radius radius". (Source: primarily nukemap, but a wiki page about a nuclear explosion states something similar)

I wonder if it would be good if we add in the 5 psi and the 1 psi part for describing an explosion having a smaller damage to surroundings.
 

Antoniofer

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Bump

I see adding the table yield/radius table is uncontroversial, but we haven't reach a clear conclusion about using different overpressure values.
 

Antoniofer

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Btw, I updated the blog, expanded it with few additional guidelines such not using the equation for combustions or AoE attacks that carries little or no pressure, and few examples of what should be used the equations. Also removed the relationship of heat and pressure, that the 0.4-0.5 hasn't beed really confirmed.
 

Antvasima

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I see adding the table yield/radius table is uncontroversial, but we haven't reach a clear conclusion about using different overpressure values.
Btw, I updated the blog, expanded it with few additional guidelines such not using the equation for combustions or AoE attacks that carries little or no pressure, and few examples of what should be used the equations. Also removed the relationship of heat and pressure, that the 0.4-0.5 hasn't beed really confirmed.

@Amelia_Lonelyheart @Armorchompy @KLOL506 @DemonGodMitchAubin @DontTalkDT @KieranH10 @TheRustyOne @DragonGamerZ913 @Migue79 @Jasonsith

What do you think about this?
 

Antoniofer

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Very well, if there's no objections and people seems to agree, perhaps the guideline should already be created, or maybe expand the former explosion ones. What do you think it would be the best, @Antvasima?
 

Antvasima

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I do not remember enough of this discussion, and calculations are not my area anymore nowadays, so I usually defer to what @DontTalkDT and the calc group members think is best.
 
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