Ongoing problems with the bombs effectiveness - Reminder for the Devs

[JG4_Qetzalcoatl]

Many months ago I saw the last information with regards to the irritating bombs effectiveness:

 

On 7/22/2020 at 4:48 AM, -DED-Rapidus said:

About bombs and the effects of concomitant explosions-the issue will be further investigated. You should not expect a quick solution, because this is primarily a matter of optimization. Plus, the durability of objects depends on the durability specified by the map creators, which also has an impact.

 

Our fighter bomber pilots having still great problems to estimate the destruction potential of their bombs. Especially the greater bombs are a great disappointment. As far as I know this is the same for both sides (red and blue).

Yesterday we did a few test bombing runs on the SLT Server. I will present you two examples, one with a screenshot.

 

First example:

We dropped bombs on 5 clusters of gasoline tanks at an airfiled. After only one was left we dropped a 1800kg and a 2400kg bomb in the middle of the tank area. Nothing happened the last cluster was still intact and visible in the big crater. At last I dropped a single 50kg bomb, scored a direct hit and this cluster was gone.......

 

Second example:

I dropped one by one 3 50kg bombs on splinter boxes. The first exploded in the box between the plane and the wall. Both sides of the wall were destroyed but the plane was intact. (Circle No. 1)

The second bomb exploded in front of the box. Nothing happend even the walls remained untouched. (Circle No. 2) The third bomb was a direct hit on the plane in the center box. The plane was completely wrecked but no crater visible. (Circle No. 3)

 

Conclusion for me - There is a problem with the bomb blast calculation which it seems the server hosts can´t resolve alone. The objects are easy destroyable with a direct hit but you won´t use big bombs in the hope of a direct hit. Instead you want to flatten a whole area. If this not works it is not fun in a game like BoS with such a high standard in all other parts. A whole bunch of the fighter bomber guys are very frustrated.

 

So it would be nice to hear something new or at least get an information update to this topic. Thanks a lot so far, you did a great job in the last years!

 

JG4_Qetzalcoatl

Edited January 28, 2021 by JG4_Qetzalcoatl

[PatrickAWlson]

Something to be aware of: static airplanes are "blocks" in the game, not airplanes.  Other items too are blocks with a damage capacity.  How easy or difficult something is to destroy is heavily dependent on the damage value assigned to that block in the mission.  When I drop things from the ME it assigns a pretty high value by default.  

 

Not saying you're wrong.  Just suggesting that the mission maker ensure that the damage values on these destructible items is appropriate.

[JG4_Qetzalcoatl]

Thanks for your clarification. But as I said the static plane or the tanks are easily destroyable by a direct hit with a 50kg bomb. So the value seems ok. Weird is the fact that a near miss by an aprox. 2000kg bomb (see 1st example) seems ineffective....?

[[DBS]Browning]

24 minutes ago, JG4_Qetzalcoatl said:

Thanks for your clarification. But as I said the static plane or the tanks are easily destroyable by a direct hit with a 50kg bomb. So the value seems ok. Weird is the fact that a near miss by an aprox. 2000kg bomb (see 1st example) seems ineffective....?

 

Bomb damage decreases more than the inverse square of the distance from the blast.

Direct hits will often destroy objects, even if the mission file had the damage value set far too high.

 

This is an issue for mission makers.

[SAS_Storebror]

11 hours ago, [DBS]Browning said:

This is an issue for mission makers.

The issue reported in the OP is not an issue for mission makers, it's definitely an issue with bomb effectivity.

I've reported it years ago already - in may 2018 to be precise - but never got any feedback and nothing ever changed.

 

Here's an example of a 1.8 tons bomb dropped right on top of a train (actively moving object, albeit standing still at the time of being bombed).

Only two cars got killed and the crater is much larger than the damage caused to the train, actually the train cars literally disappear inside the crater:

 

 

 

Next example is a 500kg bomb dropped on another (moving) train.

Impact was some 30m in front of the locomotive.

Result: Locomotive left undamaged, tender left undamaged, following three cars left undamaged, and fourth car killed.

 

And finally, here's a 100kg bomb dropped on the last car of a train, causing exactly the type of damage you'd expect: Last three cars killed, remaining train untouched:

 

It is something we keep experiencing a thousand times ever since: Small bombs (up to ~250kg) seem to work fine, above that, the larger it gets, the weirdest the results.

Note: All of this happened online. Offliners might see different things as we might be seeing another incarnation of a netcode issue.

 

Mike

[[DBS]Browning]

3 hours ago, SAS_Storebror said:

The issue reported in the OP is not an issue for mission makers, it's definitely an issue with bomb effectivity.

I've reported it years ago already - in may 2018 to be precise - but never got any feedback and nothing ever changed.

 

Here's an example of a 1.8 tons bomb dropped right on top of a train (actively moving object, albeit standing still at the time of being bombed).

Only two cars got killed and the crater is much larger than the damage caused to the train, actually the train cars literally disappear inside the crater:

 

 

 

 

It is something we keep experiencing a thousand times ever since: Small bombs (up to ~250kg) seem to work fine, above that, the larger it gets, the weirdest the results.

Note: All of this happened online. Offliners might see different things as we might be seeing another incarnation of a netcode issue.

 

 

So in this example, Lets assume the train cars are 8m long. That's a total guess and I'll be happy to change it if someone can provide a more accurate length.

 

That puts the craters centre at about 20m away from the train car that is partly obscured by the crater.

I'll assume that the bomb detonates entirely on the surface (actual second war bombs had enough delay on their instant fuses to partly bury themselves to between 10cm (0.0005 second delay) and 40cm (0.002 second delay) depth for a bomb falling at 500mph. Such burying dramatically reduces explosive power even at the shallow end of that scale, but I'll continue with the best case scenario of the bomb exploding on the surface.).

 

The DDESB Blast Effects Computer gives me a Positive Phase Impulse of 134.9 psi-ms at the centre of the partly obscured train car for a 2000kg TNT explosion.

A jeep requires an absolute minimum PPI of 90 psi-ms to be overturned, and it is likely to be drivable once flipped back over. Severe damage to jeeps and trucks does not occur until 500 psi-ms is reached according to Glasstonc (1964), or between 250and 350 psi-ms according to Ethridge (1961).

 

At 134.9 psi-ms, it is unlikely that a train wagon would be overturned or suffer serious damage at this range. Shrapnel damage is insignificant for such a target also.

 

What is absolutely wrong is the size of the crater. It should not be in excess of 6.5 meters in diameter, even for relatively soft, sandy soil. Here we see a crater around 40m in diameter. Nothing non-nuclear that can be carried by a plane can make a hole this size.

Delayed fuses will cause craters a little under double the size of non-delayed fuses.

 

My sources are:

Explosion effects computation aids L.E Fugelso 1972 Link

Estimates  of  crater  dimensions  for  near-surface  explosions  of  nuclear  and  high-exploslve  sources Henry F. Cooper, Jr. 1976 Link

The DDESB Blast Effects Computer Link

Edited January 29, 2021 by [DBS]Browning

[SAS_Storebror]

I love it how every time, regardless how abstruse of a bug is being reported, immediately someone comes around, picks a single bit of it and provides a lengthy explanation how everything we've witnessed is just normal.

 

Now in essence what you're saying is that the crater of a 1.8 tons bomb should not exeed 6.5 meters in diameter and a train's fuel car (that's what the first undamaged car is, plain to see on the image) being about 20 meters (estimated) off the explosions' center, should remain undamaged.

 

Why don't you tell that to the people having suffered the impact of a 850kg V1 doodlebug warhead?

 

Mike

[[DBS]Browning]

49 minutes ago, SAS_Storebror said:

Now in essence what you're saying is that the crater of a 1.8 tons bomb should not exeed 6.5 meters in diameter and a train's fuel car (that's what the first undamaged car is, plain to see on the image) being about 20 meters (estimated) off the explosions' center, should remain undamaged.

 

That's not exactly what I (or rather the sources I used) say, but it's not far.

The crater for the bomb should not exceed 6.5m for a surface explosion, but for a delayed action bomb, it may be a little less than double that.

A train car 20m away from a detonation equivalent to 2,000kg of TNT might not be "undamaged", but it will be free of severe damage and won't be flipped.

 

The force of an explosion drops rapidly with distance.

These measurements are extremely well understood and documented and are a far, far better way to measure an explosion's effects than looking at a photo and extrapolating based on a hunch.

 

It's also worth noting that masonry walls are very weak to forces that are out of plane with the wall. A masonry wall at the distance of the railway car may not have faired so well. I'm looking up numbers at the moment and will edit this post shortly.

Edit: The best data I can get at a glance is for concrete walls. Not much available for brick masonry.

Edited January 29, 2021 by [DBS]Browning

[SAS_Storebror]

4 hours ago, [DBS]Browning said:

These measurements are extremely well understood and documented and are a far, far better way to measure an explosion's effects than looking at a photo and extrapolating based on a hunch.

If that floats your boat...

Meanwhile, this is what 10kg of yellow RDX do:

 

And you keep telling me that a fuel tank 20m off the detonation of a 1.8 ton bomb is safe from destruction.

 

Mike

[[DBS]Browning]

3 hours ago, SAS_Storebror said:

And you keep telling me that a fuel tank 20m off the detonation of a 1.8 ton bomb is safe from destruction.

 

Glasstonc (1964) is telling us that he found that 500 psi-ms is required to severely damage a truck.

Ethridge (1961) is telling us between 250and 350 psi-ms is required.

Both of these results were achieved through experimental data. Real trucks, real explosives.

 

Fugels et. al (1972) is telling us that at a range of 24m the Positive Phase Impulse of 2,000kg of TNT detonated in open air at sea level at an air temperature of 15C is 134.9 psi-ms.

That result is based on extrapolation of data from real explosions.

 

I'm telling you that a train car is likely to withstand explosions slightly better than a jeep or truck and that an impulse of 134psi-ms is not going to cause it severe damage.

 

Pictures of bomb debris are not a good way to guess at these things, however, as it appears to be the only way you can understand such things, consider this image from a US bombing raid on Bucharest.

 

 

There is no way to know the size of the bomb, but in general the US used 500lb, 1000lb, and 2000lb bombs for such targets.

 

Or consider this image from Limburg rail yard which shows massive destruction from many large bomb blasts, but also shows rail cars without severe damage well within 20m of bomb craters. Some even within 10m.

 

 

 

Edit: Not that it's especially relevant to the discussion, but the image you posted is from the 1993 bombing of the Bombay Stock Exchange in which 30kg, not 10kg of RDX was used in the buildings underground carpark. Source

 

Edited January 29, 2021 by [DBS]Browning

[sniperton]

9 hours ago, SAS_Storebror said:

I love it how every time, regardless how abstruse of a bug is being reported, immediately someone comes around, picks a single bit of it and provides a lengthy explanation how everything we've witnessed is just normal.

I love it too. Do angels have belly buttons? Cheers, I'm out.

[Mitthrawnuruodo]

17 hours ago, [DBS]Browning said:

It's also worth noting that masonry walls are very weak to forces that are out of plane with the wall. A masonry wall at the distance of the railway car may not have faired so well. I'm looking up numbers at the moment and will edit this post shortly.

 

This 1945 US document (forgive me if you've already seen it) gives the blast effects of various bombs on "German load bearing wall construction". With a 4,000 lb Light Case (LC) bomb, total demolition occurs to a radius of 37 m. However, it is noted that the LC bombs are more effective than other bombs in terms of blast damage. A 2,000 lb General Purpose (GP) bomb causes total demolition to 16 m. These results are achieved with instantaneous fuses and detonations on or above the ground.

 

Depending on the type of bomb and the amount of penetration into the ground, fragment damage to railway rolling stock may be significant. Fragments from a 500 lb GP bomb are likely to perforate 1/4" mild steel as far as 25 m away. Of course, this leaves us with a slightly more esoteric question - at what point is it reasonable to count a train car as "destroyed"?

 

 

Edited January 30, 2021 by Mitthrawnuruodo

[[DBS]Browning]

5 hours ago, Mitthrawnuruodo said:

 

This 1945 US document (forgive me if you've already seen it) gives the blast effects of various bombs on "German load bearing wall construction". With a 4,000 lb Light Case (LC) bomb, total demolition occurs to a radius of 37 m. However, it is noted that the LC bombs are more effective than other bombs in terms of blast damage. A 2,000 lb General Purpose (GP) bomb causes total demolition to 16 m. These results are achieved with instantaneous fuses and detonations on or above the ground.

 

Depending on the type of bomb and the amount of penetration into the ground, fragment damage to railway rolling stock may be significant. Fragments from a 500 lb GP bomb are likely to perforate 1/4" mild steel as far as 25 m away. Of course, this leaves us with a slightly more esoteric question - at what point is it reasonable to count a train car as "destroyed"?

 

 

 

Yup, it's one I'm aware of, but haven't looked at recently. I think I even referenced it in another thread a while back.

 

Bomb fragments are interesting. I've got a source somewhere that is concerned with ammunition storage that suggests whist dangerous, fragments are not a massive issue for personnel.

At ranges where the number of fragments per square metre are high enough to make a hit on a human likely, the blast is close enough to do more damage through overpressure of the lungs and ears.

 

Even slight ground penetration dramatically reduces the number of fragments travelling close to the ground. Although it looks like burying isn't as much of an issue as I had assumed.

"US Aerial Armament in WW2" by William Wolf is very much a secondary source, but it's also my only source for the action sped of period instant fuses.

 

 And from here we can get an idea of bomb speeds, although presumably for dive bombers we must add the vertical speed of the plane also:

 

From this we can see that burying of instant fuse bombs is anywhere from near complete to insignificant depending on the speed of the bomb.

This data is for 500lb bombs and changes quite a bit with weight. Some larger bombs are capable or reaching super-sonic speeds before impact.

I think most drops from medium to low altitude, as we tend to see in IL-2, are going to have only a little burying.

 

So damage to a train car from fragments at 20m? Well, there are certainly going to be some small holes in the wood. Perhaps as many as five per square meter, although fewer lower to the ground. Structural steel parts are very unlikely to be damaged. Is that enough to call it destroyed? As you say, an esoteric question. You could argue that a single fragment can destroy a liquid carrying train car by causing a leak and making it useless for it's job, or you could argue that so long as it is upright and able to roll on the rails, it's not destroyed. It's perhaps better to think in terms of how seriously damaged it is and for this case, I don't think you could argue that fragmentation is likely to severely damage it.

 

Masonry walls are different altogether. They are very week to out-of-plane forces and very strong to in-plane forces. In addition, they cause the blast to reflect upon it's self which multiplies it's force. Narrow streets can cause channelling and even amplification of blasts, resulting in higher pressures at distances you might not otherwise expect. I have sources on the modelling of such effects that are far too complex for me to understand. Masonry debris can also contribute far more to the damage done than bomb fragments.

I'd love for a source for a ball-park on the pressure impulse required to bring down masonry walls, but I'm unable to find anything. Perhaps I could come up with a number by working backwards from the source you linked. At any rate, I'm sure the source you linked is a reliable guide, but it only applies to masonry, we can't use it to say, for example, "total demolition of a building occurs to a radius of 40m, therefore a truck/tank/human/etc. will certainly be destroyed at 25m". Not that I think you were trying to make such a point.

 

Edited January 30, 2021 by [DBS]Browning

[SAS_Storebror]

On 1/29/2021 at 11:31 PM, sniperton said:

Do angels have belly buttons? Cheers, I'm out.

They do, I hear them ringing.

And anyone who thinks that fuel tank's metal sheet is safe from a 1.8 tons bomb blast 20 meters away is welcome to join us here in germany on the next defusing of a WWII bomb and watch it from 20m distance.

Here are some images of a 500lb one, full story here (sorry it's in german), - bomb fragments caused severe damage within a radius of 300 meters:

https://www.welt.de/regionales/muenchen/gallery108852872/Schwabing-nach-der-Explosion-der-250-Kilo-Bombe.html

 

 

 

 

 

 

 

 

 

 

And since everyone has taken firm positions, I'm out as well.

This will get us nowhere. The nay-sayers have taken over long time since.

 

Mike

[Mitthrawnuruodo]

 

1 hour ago, SAS_Storebror said:

And anyone who thinks that fuel tank's metal sheet is safe from a 1.8 tons bomb blast 20 meters away is welcome to join us here in germany on the next defusing of a WWII bomb and watch it from 20m distance.

 

I'm not quite as tough as 1/4" to 1/2" thick steel yet, so I'll leave it to the tank car for now.

 

The explosion looks spectacular, but I only see a crater, many broken windows, and several fires caused by flying straw (if I'm reading the German correctly). No significant structural damage or demolition of nearby buildings. The tank car at 20 m would likely be safe from the blast.

 

For the record, I'm commenting on the 500 lb bomb in the article, not an SC1800.

 

1 hour ago, SAS_Storebror said:

bomb fragments caused severe damage within a radius of 300 meters:

 

The caption says that bomb fragments had flown up to 300 m. It's not controversial that bomb fragments can fly very far. However, the chance of a train car getting hit and perforated at that range is tiny, so this matters little for modeling the average case.

 

21 hours ago, [DBS]Browning said:

It's perhaps better to think in terms of how seriously damaged it is and for this case, I don't think you could argue that fragmentation is likely to severely damage it.

 

Agreed. Aside from tank cars, locomotive boilers, and particularly sensitive freight, it seems unlikely that a few fragment perforations would matter much. The main reason I brought it up is that the cited document specifically mentioned rail targets as a possible application of the 1/4" and 1/2" mild steel perforation results.

Edited January 31, 2021 by Mitthrawnuruodo

[Luftschiff]

Real world effectiveness aside, something is definitely iffy with the bomb damage calculations at present, a 50 kg bomb and a 1000 kg bomb dropped at the same distance from hard or soft targets will currently do the same amount of damage - and a 50kg bomb generally appear to do MORE damage than a 500kg bomb at the same distance. I will need to record new tracks as I lost my last tests in a disk move, but just looking at OP's tests I think at current it must definitely be considered a bug just based on how strange the damage effects are. The car furthest from the blast being the only one damaged? 

I like that 50's reclaimed their usefulness in the latest overhaul, but it came at the expense of making every other bombload if not useless then tactically pointless. Bombs and standard loadouts grew larger over the course of the war, they were clearly useful. In game, not so.

Even if we assume the calculations are flawlessly realistic, we must also consider that the nature of our targets are not. We attack indestructible villages and towns with maybe ten destroyable buildings in it, no people or infrastructure, no purpose to anything but a direct hit and destruction - and no points awarded until all those exact buildings or vehicles have been destroyed. There's no such thing as reducing effectiveness, no such thing as causing casualties and hurting morale. you can't destroy a road or carpet a runway to prevent its use, you need to score direct hits with 2400 kg bombs to destroy a single truck. This IS an issue with the game right now, especially for those few who still enjoy flying bombers. It is a discussion worth having.

Edited January 31, 2021 by Luftschiff