Thread on bomb loads

[Lemurs!]

Hi all,

I have heard a rumour that Matrix released some comprehensive data on how bomb loads work, especially in regard to 2e and 4e bombers.

I just searched for this and could not find it; if you know where this is i would like to read it and would appreciate a point in the right direction.

Thanks,
Mike

[Pascal_slith]

If they did, I would request that it be added to the FAQ at least, if not in a revised manual.

[witpqs]

Here you go. The thread is called Level Bombers in the main WITP forum. Search didn't work for me either, but I kind of remembered what it was called and skipped down to find it.

Hello...

Having written the code for this, I have some insight into how it works. Bombers carry the outload listed, such as 4x500 lb or 1xtorpedo.

If attacking land based targets, they carry the same thing. Such as 4x500 lb or 1xtorpedo=2x500 lb (the code trades torpedoes for bombs). The aircraft maximum load value is only used for calculation of airfield size needed from which to operate.

If scheduled to carry 500lb GP bombs and if the plane normally carries at least four of them and if the crew has at least the minimum required experience and if the crew makes an experience roll and if the squadron leader makes a skill roll and if the airfield is large enough and if there is enough supply, then the aircraft may exchange each 4x500lb GP bombs for 2x1000lb GP bombs. If the crew has more experience and passes a harder roll and if the base is at least a certain size and has more supply and is carrying at least 4x1000lb GP bomb, then the aircraft may exchange each 4x1000lb GP bombs for 2x2000lb bomb.

Patrol aircraft on naval search commonly carry torpedoes. Those same aircraft, if on anti-submarine patrol exchange those torpedoes for bombs.

Hope this Helps...

Michael Wood

< Message edited by Mike Wood -- 1/16/2006 2:15:33 PM >

+++++++++++++++++++++++

This one was about bombing land targets:

Hello...

No. Works out the same. The 500 pounders give twice as many chances to hit, doing one half damage. 2x500 of one or 1x1000 of the other.

Do not recommend change. We did it the way we thought best. But, I wrote the editor for you to make changes, as you might, so go to it, if you like.

Bye...

Michael Wood

+++++++++++++++++++++++++

Hello...

Well, "...bombing a land target 10,000lbs of payload..." never occurs.

Bombing land based targets with planes, bombarding them by sea or attacking by land all work the same way, in this regard. Each weapon or bomb makes an individual attack. So, dropping 8x250 lb GP bombs makes 8 attacks and 4x500 lb GP bombs makes 4 stronger attacks. Note that bombers normally carrying 500 lb GP bombs never carry 1000 lb GP or 2000 lb GP bombs when attacking land based targets. Switch to 1000 lb and 2000 lb is only made for naval targets.

Bye...

Michael Wood

+++++++++++++++++++++++++++++++

And one from Mr. Frag:

quote:

So if I changed ...um...



Just remember that these special effects are coded to device slots, so when you adjust them, think device adjustment, not just aircraft adjustment or you'll have some unintended effects.

[Sardaukar]

That is very important information. It seems to work totally different than I was understanding it. Good to know when editing aircraft loads.

[Lemurs!]

Yea, that's interesting to know. I had been told as of release that the listed load out was only used in naval attacks while the max load number was used to make land/base attacks.

Would have been nice if someone had mentioned this before now, as i started this mod the day after the game came out and it is central to the changes i made to aircraft. grr..

Well, i guess i will test to see if this is true. I will launch 1 group raids against Wake with B29's with a max bombload of 1000lbs and B29s with a max bombload of 20,000lbs and see if it makes a difference.

But, probably i will have to redo all of my bomb load work. I had lowered the listed weapon loads for heavy bombers because of the ridiculus results they get in port bombing.

thanks for finding the data.

Mike

[Nomad]

I will be very interested in your tests, I also thought it worked like you said.

[el cid again]

1xtorpedo=2x500 lb

Weight wise, the trade should be 3 500 pound bombs for one torpedo. Unless limited by hard points, this should be the standard. I wonder why it is not?

[el cid again]

If scheduled to carry 500lb GP bombs and if the plane normally carries at least four of them and if the crew has at least the minimum required experience and if the crew makes an experience roll and if the squadron leader makes a skill roll and if the airfield is large enough and if there is enough supply, then the aircraft may exchange each 4x500lb GP bombs for 2x1000lb GP bombs. If the crew has more experience and passes a harder roll and if the base is at least a certain size and has more supply and is carrying at least 4x1000lb GP bomb, then the aircraft may exchange each 4x1000lb GP bombs for 2x2000lb bomb.

Apparently this simple model thinks it is better to carry heavy bombs. But that is not always the case. The Vulcan hitting Port Stanley dropped 1000 pound bombs - 21 of them - to maximize the chance of a hit. Just one hit the runway. Imagine if it had carried 10 2000 pound bombs instead - it would have missed (the hit was no 21 of the string - the very last bomb - the center of the pattern was off target). Bomb size should be a function of target type, and damage should not be directly proportional to bomb size, but to the square root of bomb size - because that is how explosions work. UNLESS you have to penetrate something, a bigger bomb is not an advantage.

[Pascal_slith]

el cid again, I'm interested in your source for bomb effectiveness, especially this square root relation. What is your book/scholarly paper source for this formula?

[witpqs]

ORIGINAL: el cid again

Apparently this simple model thinks it is better to carry heavy bombs. But that is not always the case. The Vulcan hitting Port Stanley dropped 1000 pound bombs - 21 of them - to maximize the chance of a hit. Just one hit the runway. Imagine if it had carried 10 2000 pound bombs instead - it would have missed (the hit was no 21 of the string - the very last bomb - the center of the pattern was off target). Bomb size should be a function of target type, and damage should not be directly proportional to bomb size, but to the square root of bomb size - because that is how explosions work. UNLESS you have to penetrate something, a bigger bomb is not an advantage.

FYI, I think in this case that was exactly the point. The 500 pounders were more or less bouncing off heavily armored battleships, so the issue of availability of bigger hammers, er - bombs - came up.

[el cid again]

el cid again, I'm interested in your source for bomb effectiveness, especially this square root relation. What is your book/scholarly paper source for this formula?

Actually, it is just physics. It is the way an explosion works. Energy dissipates as the square of the distance. For a soft target (which is something not hard like made of concrete or steel - wood is more or less soft), the damage area is inversely proportional to the distance from the detonation, squared. A larger bomb does release more energy - actually not in direct relation to its weight - but in direct relation to the explosive on board multiplied by a factor for the efficiency of the explosive (thus, for example, Torpex is worth more pound for pound than TNT). But the amount of exposive is roughly proportional to the bomb (or shell) weight - not a horrible simplification for our purposes if you don't want to look up the details of each bomb. Anyway - a bigger bomb is useful ONLY when there is something that NEEDS a bigger bomb as a target. For most targets, you are better off dropping more smaller bombs. [This is why bomblets are so popular]. It appears we have a model that says "two attacks by 500 pound bombs = 1 attack by a 1000 pound bomb" and, in general, this is false. There is a reason our standard bomb load was 500 pound bombs, not 2000 pound bombs. The chances of a hit by fewer bombs is significantly lower. But IF you score a hit, the bigger bomb usually does not do as much damage as more than one (even just two) smaller hits. On the other hand, there are exceptions, and you also can get lucky, if you start a fire (common) or cause an explosion (rare). A bigger bomb matters when hitting a battleship - and the 16 inch shells dropped from Kates at Pearl Harbor were effective. In that case, you needed something bigger than even a thousand pounder to reliably penetrate a deck. And one bomb got lucky - causing a secondary explosion which sank Arizona. No smaller bomb would have done that.

[treespider]

ORIGINAL: el cid again

el cid again, I'm interested in your source for bomb effectiveness, especially this square root relation. What is your book/scholarly paper source for this formula?

Actually, it is just physics. It is the way an explosion works. Energy dissipates as the square of the distance. For a soft target (which is something not hard like made of concrete or steel - wood is more or less soft), the damage area is inversely proportional to the distance from the detonation, squared. A larger bomb does release more energy - actually not in direct relation to its weight - but in direct relation to the explosive on board multiplied by a factor for the efficiency of the explosive (thus, for example, Torpex is worth more pound for pound than TNT). But the amount of exposive is roughly proportional to the bomb (or shell) weight - not a horrible simplification for our purposes if you don't want to look up the details of each bomb. Anyway - a bigger bomb is useful ONLY when there is something that NEEDS a bigger bomb as a target. For most targets, you are better off dropping more smaller bombs. [This is why bomblets are so popular]. It appears we have a model that says "two attacks by 500 pound bombs = 1 attack by a 1000 pound bomb" and, in general, this is false. There is a reason our standard bomb load was 500 pound bombs, not 2000 pound bombs. The chances of a hit by fewer bombs is significantly lower. But IF you score a hit, the bigger bomb usually does not do as much damage as more than one (even just two) smaller hits. On the other hand, there are exceptions, and you also can get lucky, if you start a fire (common) or cause an explosion (rare). A bigger bomb matters when hitting a battleship - and the 16 inch shells dropped from Kates at Pearl Harbor were effective. In that case, you needed something bigger than even a thousand pounder to reliably penetrate a deck. And one bomb got lucky - causing a secondary explosion which sank Arizona. No smaller bomb would have done that.

If you are interetsed in blast effects:

There are two main effects which can cause damage to targets: the high energy fragments of the casing and the shock (or blast) wave. Warheads are usually designed to maximize one of these effects. Fragments tend to be lethal to a greater range than the blast effects, but it depends on the particular target. Aircraft are particularly vulnerable to fragment damage as are personnel. On the other hand, buildings can only be brought down by extensive blast effects. We now turn to a detailed account of each type.


Blast Effects

The rapid expansion of the gaseous products after the casing has burst creates a shock wave. The shock wave is an acoustic wave like ordinary sound, but of limited duration and great energy. Recall that the energy of the acoustic wave was a function of the amplitude, or peak pressure. In shock waves, the peak pressure is achieved only once, and is called the peak overpressure. The peak overpressure is reached very quickly as the shock wave passes, after which the pressure subsides more slowly.


As the wave passes the pressure oscillates one or more times between positive and negative phases. When the pressure is above the ambient, the shock wave is considered to be in the positive phase. The opposite condition is called the negative phase.

Due to the pressure differential within the shock wave, the air will flow from high to low pressure. This creates a blast wind, which can be of substantial velocity, well over 100 mph. The blast wind only lasts for a fraction of a second and changes direction during the negative phase. As the wind flows against objects, they will feel dynamic pressure from the drag. The dynamic pressure felt by an object follows the familiar equation for drag:



Pdyn = Cd ½rv(2), (2) =squared



where:
Cd is the coefficient of drag for the particular object,
r is the density of air (normally ~1.2 kg/m3) , and
v is the velocity of the blast wind.

Figure 2. Peak overpressure and dynamic pressure in a shock wave.

[treespider]

Predicting Blast Effects

Due to the complex nature of explosions, it is not possible to easily predict the magnitude of these blast effects. However, there is a vast collection of experimental data from the explosion of 1 kg of TNT, which has been chosen as the reference explosion. The values for an arbitrary explosion can be found be relating it to the reference explosion through a relation known as the scaling law. It relates the distances at which the same effect will be felt for different explosive amounts. The scaling factor is W(1/3), where W = the equivalent amount of TNT (in kg) and (1/3) = to the third. W is found by multiplying the mass of the explosive by its relative strength (RS). Explicitly:




dW = do W(1/3)




where:
do is the distance from 1 kg TNT
dw is the distance from the W kg of TNT equivalent.






Example: If a particular peak overpressure, (example: 1.5 psi) is felt at 5 m from a 1 kg TNT explosion (the reference), estimate how far away from a 10 kg PETN explosion, the same effect will be felt.




The RS for PETN is 173% (from the Berthelot approximation).

W = 10 kg 1.73 = 17. 3 Kg

The scaled distance is therefore = (17.3)1/3 5 m = 12.9 m

The same scaling law will also hold true for dynamic pressures.

The peak overpressure and dynamic pressures are found from the graph in Figure 3.

Figure 3. Peak overpressure and dynamic pressure for 1 kg TNT.



Example: Calculate the peak overpressure and dynamic pressure felt by a person facing a blast of 10 kg of TNT equivalent, standing 5 meters away.




To use the graph, the distance must be scaled down to the reference condition.

do = dw /W1/3

do = (5 m)/(10)1/3 = 2.3 m

Using the graph,

peak overpressure = 25 psi
dynamic pressure = 2.5 psi

[Lemurs!]

Yes, i am curious why this is called 'max bomb load' if it has nothing to do with bomb load.
Why not call this variable 'min airfield size' which would actually be usefull for us players? I don't know anout the rest of you but my first couple games were all about having bombers at the wrong size base.
Having this be clear on a unit screen would be nice.

Okay, also, does this value effect fighters at all? Can i set every fighter to 1,000,000lb max bomb load?

Mike

[el cid again]

Due to the complex nature of explosions, it is not possible to easily predict the magnitude of these blast effects. However, there is a vast collection of experimental data from the explosion of 1 kg of TNT, which has been chosen as the reference explosion. The values for an arbitrary explosion can be found be relating it to the reference explosion through a relation known as the scaling law. It relates the distances at which the same effect will be felt for different explosive amounts. The scaling factor is W(1/3), where W = the equivalent amount of TNT (in kg) and (1/3) = to the third. W is found by multiplying the mass of the explosive by its relative strength (RS). Explicitly:

There is also a substantial body of data on 1 kiloton of explosives. We did this during the 1980s when it became apparent that the USSR had done extensive work on surviving nuclear explosions. 1 kt was chosen as a reference point - although in the event about 600 tons of explosive was used - because it was worth more than 1 ton of TNT per ton. This material was published by Boeing.

[el cid again]

Okay, also, does this value effect fighters at all? Can i set every fighter to 1,000,000lb max bomb load?

Code is dumb. The most likely option is that ALL planes will interpret ANY number in this field the SAME way. That is, a transport will treat cargo weight as a bomber treats bomb load! And a fighter will treat any bomb load the same way too. It COULD be something else - but that would require a branch or if in the code. It seems unlikely since it makes some sense to keep it simple in this case. I have no basic problem with the reasoning used - it is more or less true. Further, I think there is something missing from what we have been told (the rule with Matrix - for one of several reasons - including that the person writing does not know everything in many cases). I think there is a difference between normal range and extended range. I don't think you carry the same load to both. Further, play experience and testing shows you DO NOT carry the same load to both - so what we were told is probably wrong. But some of what we observe is also hard coded by type - thus a Kate has special code that may not exist for any other type. Similarly, transports probably do not carry the same load to both ranges. And I suspect fighters do not carry bombs to extended range at all. [They shouldn't either]

[Andy Mac]

Wont messing about with max load mess up the max amount bombers can carry when acting as supply transports?

[witpqs]

el cid,

Matrix has stated (including in the manual) that extended range does cut the bombload. The discussion that I cut and pasted was Mike Wood answering specific queries. I did not paste the questions because it got kind of convoluted.

[el cid again]

Wont messing about with max load mess up the max amount bombers can carry when acting as supply transports?

Well - yes - except I am not sure "mess up" is the right word?
First - it is designed to dictate the b ase size - so we are fixing that.
Second - if the cargo is heavy enough - it is adjusting cargo right.
One can carry shells for example instead of bombs - or reload torpedoes - which are pretty dense. While it is not typical for cargo density it helps fix the problem that cargo planes don't really list their overload capabilities. It is a compromise - and we don't know if when acting as transports this value is used as such, divided, or ignored (and normal bomb load used)? Wish we knew - but we don't.

[Mike Wood]

Hello...

Maximum load does dictate transport capability. Now you know.

Bye...

Michael Wood

ORIGINAL: el cid again

Wont messing about with max load mess up the max amount bombers can carry when acting as supply transports?

Well - yes - except I am not sure "mess up" is the right word?
First - it is designed to dictate the b ase size - so we are fixing that.
Second - if the cargo is heavy enough - it is adjusting cargo right.
One can carry shells for example instead of bombs - or reload torpedoes - which are pretty dense. While it is not typical for cargo density it helps fix the problem that cargo planes don't really list their overload capabilities. It is a compromise - and we don't know if when acting as transports this value is used as such, divided, or ignored (and normal bomb load used)? Wish we knew - but we don't.