Rocket Artillery to inaccurate?

[Bullethead]

Scipio said:

<blockquote>quote:</font><hr>The numbers mean that 50% of the rockets hits a square of x m lenght and y m width

Nebelwerfer 41 (150mm) : 130m x 80m

Wurfgerät 40/41 (280mm): 160m x ? m

21cm Nebelwerfer 42 (210mm) : 500m x 130m

30cm Nebelwerfer 42 (300mm) : 175m x ? m

<hr></blockquote>

I just did some testing on CM's German rockets. The test consisted of firing each type of rocket FO (150mm, 210mm, and 300mm) with 100 rounds at a bullseye target made of rings of brush tiles 100m apart. In the center was a TRP and the FOs had LOS to the TRP.

All CM rocket FOs produced the same pattern. It was roughly circular. On average, about 80% of all rounds landed within 200m of the TRP, 15% landed within 300m, and 5% landed within 400m. The 50% cut-off is therefore within 200m of the point of aim for all types of German rockets in CM.

I have done similar tests in the past but that was several patches ago. I was surprised to see a change this time. Previously, the rocket impacts were more or less uniformly spread over a 750m diameter circle. But now, there is a distinct clustering in the center.

Anyway, it appears that CM rockets are at least as accurate on the X axis as they were in real life, if not more so. And I don't think the Y axis of the pattern is a problem, either.

Consider that each rocket barrage was fired by 4 or so launchers, which were spaced like 20m apart on a line perpendicular to the line of fire. Thus, the whole battery's pattern would be about 160m wide (40m outboard of each end launcher, which are 80m apart). This would result in a roughly circular are square pattern for the whole battery when combined with the X-axis dispersion of 130m. And remember, this (real life numbers) is for only 50% of the rockets. In my test, more like 60-70% of the rounds landed within this distance.

Of course, while CM's modeling works for the 150mm, it appears a bit too tight for the larger rockets. But still, CM's rockets seem a bit more accurate than the best performance of real life. Thus, saying they're "Napoleanic" is rather incorrect.

[Tero]

Originally posted by Jeff Duquette:

Tero: I suspect the nomenclature is perhaps different in the Finish Army.

Not really. I served in the coastal arty so the nomenclature is known to me. I just want to know the actual mean average and mean deviation, statistically speaking. How did you come up with the 50% zone ? Also, does the calculations apply to a single tube or a whole battery ?

It basically defines a weapons shot pattern based purely on systematic error.

Disregarding such quantifiable, non-athmospherical aspects as barrel wear. To the best of my knowlegde most, if not all (well, at least the Finnish army did/does), armies kept a log book on arty pieces so they could monitor barrel wear and alter firing solutions to match it and get better accuracy.

Of the 50 rounds fired 25 will in theory fall on one side of the mean range line (short\under) and 25 will fall on the other side of the mean range line (long\over). Same deal with deflection error. Twenty-five rounds will fall to the right of the mean deflection line, and 25 will fall on the left of the mean deflection line.

How many of them impact at the actual, absolute, target point ? By your reconing only 4 rounds come even close. 46 impact anywhere within the 50% zone BUT the target point proper. And the rest (50) outside it. Does not sound viable.

I have seen a 4 gun battery hit a target the size of a rowing boat at 2000 meters with the fourth salvo. Field artillery works a bit differently, I know, but the idea is (as I understand it) to get the 100% zone as tight as possible. IIRC the Finnish arty used a square of 100x50 meters as the basis for its 100% zone at the battery level.

The apex of the mean deflection line and the mean range line is the MPI: Mean Point of Impact....loosely speaking the MPI can sort of be thought of as the centroid of the target area you are trying to suppress or destroy.

The actual shot pattern would trend toward an elongated elliptical shape. However a rectangular area is easier to quantify and I suppose close enough for HE work. It’s all based upon a normal distribution so I suppose if you were so inclined you could figure out the 2% zone if you really wanted to.

What is the firing pattern you are assuming: all guns pointing at the target point, guns pointing at the target point by the section or guns pointing at the target zone by the battery ?

[Tero]

Originally posted by Jeff Duquette:

I dunno. Could be. I have some old US Naval Range and Ballistic Tables laying about here somewhere. From the late 30’s. As I recall they include firing tables for calibers up to 14” guns.

Seems to me like the fall patters in CM are directly connected to the caliber. The bigger the caliber the wider the dispersion pattern.

This could be…like I say I have not played with CM’s rocket artillery much. I am typically on the receiving end of it

I usually pick a 81mm mortar over them.

I am speaking purely in generalities and attempting to explain that WWII conventional artillery typically delivers a much tighter pattern of rounds than WWII rocket artillery.

Yes. But both were after all area fire weapons for the most part and you could blanket a target are more effectively more rapidly with a rocket barrage than a conventional arty barrage. Generally speaking.

I am less interested in the implications to specific wargames. Like I said above; "As to whether rockets are being accurately portrayed in any wargame, IMHO I think a wargame should reflect a tendency toward much larger dispersion zones for rocket barrages relative to more conventional artillery barrages".

But should the rocket arty get handicapped because of them ?

Even than I suspect I would want to hear what the designers intentions were or how they went about developing random dispersion patterns for artillery fire.

One thing I seem to remember about them was something about preventing gamey use of arty as the main force.

This really should not be an exercise in mumbo-jumbo.

There can be no debate if the nomenclature is not explained and equalized. You should know that.

[Tero]

Originally posted by Berlichtingen:

Not really. Rocket is a rocket. What I was getting at ws that even with the Cobra's ability to directly aim the rockets, they flew all over the place. change that to less streamlined rockets and fire them indirectly and they are going to scatter even more

AFAIK FFAR's are fin stabilized. They are also meant to be fired at LOS ranges. What is their max range ?

Also, is there a diffrence in the MV of the FFAR and the Nebelwerfer rocket ?

[Dan Robertson]

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

GPS guided shells? Isnt cost a problem?<hr></blockquote>

Not really, modern electronics is always reducing in price. Chemicals rarely do, it still costs nearly as much money to process propellant and explosives as it did in WWII.

IIRC the cost of a sabot round for the 120mm gun is $5000. I would expect a cluster artilery shell to cost even more.

So the price of adding a small about of digital equiptment is not going to be that high.

The advantage you get is that with a shell that is accurate to tens of meters. If it is bursting shell this is well within its leathal zone.

This means if you want mine a road with artilery deliverd mines you only need one or two rounds. For attacking mobile military targets using GPS will make artilery much more capible and cheaper.

Conventional rounds do still have their place, they can blast out deep bunkers which cluster munitions cannot reach, intense artilery fire will also clear through mine fields. Where as instense cluster munitions fire will actually create a low level minefield from unexploded munitions.

If you want to see the effects get about 50 2inch morters to fire on one target at a time. For MLRS get 644 to do it at one time.

[Jeff Duquette]

<blockquote>quote:</font><hr>Tero Said: Not really. I served in the coastal arty so the nomenclature is known to me. I just want to know the actual mean average and mean deviation, statistically speaking. How did you come up with the 50% zone ? Also, does the calculations apply to a single tube or a whole battery ?<hr></blockquote>

As I indicated this information is laid out in TFT’s….Tabular Firing Tables. A weapons dispersion is determined by test firing. As I recall British Coastal Artillerists were the first folks to start employing something along the lines of firing tables. Surely you are familiar with firing tables. I had thought artillerists that rely on “Kentucky-Windage” died away sometime during WWI.

An example of a circa-WWII TFT for 105mm Howitzer:

http://www.geocities.com/jeffduquette/stuff10/artyTFT.html

As my previous description does not seem to be taking hold with you I would suggest consulting your Field Manual for Coastal Artillery Gunnery. If it is laid out like US ARMY Artillery FM’s there should be a decent write-up on dispersion and exterior ballistics. In very lay terms the 50% zone is the length and width of two Probable Errors. One to the right of the mean deflection line…one to the left…one long of the mean range line and one short of the mean range line. Add um all togeather and you get the dimensions of the 50% zone.

In the following schematic Each “X” represents one probable error…the “O” is the MPI. So for range error in which the line of fire is parallel to the line of X’s…

line of fire -->..X-X-X-X-O-X-X-X-X

50% of the rounds fall within the two X’s immediately adjacent to the “O”

82 percent will impact within the four X’s immediately adjacent to the “O” (the two on the right of the O and the two on the left of the O)

96 percent will impact within the six X’s immediately adjacent to the “O” (the three on the right of the O and the three on the left of the O)

and 100 percent will include all eight X’s

Same again for deflection error. Each X equals one deflection probable error. The line of fire is perpendicular to the line of X’s.

....................X

....................X

....................X

....................X

line of fire -->..O

....................X

....................X

....................X

....................X

<blockquote>quote:</font><hr>To the best of my knowlegde most, if not all (well, at least the Finnish army did/does), armies kept a log book on arty pieces so they could monitor barrel wear and alter firing solutions to match it and get better accuracy.<hr></blockquote>

This is my understanding as well.

<blockquote>quote:</font><hr>How many of them impact at the actual, absolute, target point ? By your reconing only 4 rounds come even close. 46 impact anywhere within the 50% zone BUT the target point proper. And the rest (50) outside it.<hr></blockquote>

I don’t recall providing my reckoning on numbers of rounds that will hit the MPI.

<blockquote>quote:</font><hr>I have seen a 4 gun battery hit a target the size of a rowing boat at 2000 meters with the fourth salvo.<hr></blockquote>

Your point on bringing this direct fire anecdote up eludes me.

<blockquote>quote:</font><hr>IIRC the Finnish arty used a square of 100x50 meters as the basis for its 100% zone at the battery level.<hr></blockquote>

100% zone for what specific weapon, firing what specific charge, and at what specific range? Sounds like your talking about a standard sheaf for a mortar platoon? I'm talking about systematic error inherent in the fire from one gun.

<blockquote>quote:</font><hr>What is the firing pattern you are assuming: all guns pointing at the target point, guns pointing at the target point by the section or guns pointing at the target zone by the battery?<hr></blockquote>

I am talking about inherent systematic error of one gun firing at a specific range, using a specific charge.

[ 11-24-2001: Message edited by: Jeff Duquette ]</p>

[Bullethead]

tero said:

<blockquote>quote:</font><hr>Seems to me like the fall patters in CM are directly connected to the caliber. The bigger the caliber the wider the dispersion pattern.<hr></blockquote>

This is incorrect. In light of the apparent changes in rocket patterns, I have just re-done my similar experiments with other weapons. This has shown that caliber has no effect on pattern. Instead, only the following variables seem to matter in CM: 1) type of weapon (gun, mortar, or rocket), 2) LOS, and 3) TRP. The results are as follows (with at least 95% of rounds in the boundaries specified):

Guns with TRP

LOS: 120m E-W x 50m N-S

No LOS: same (but the 5% beyond this is further out than with an LOS)

Guns without TRP

LOS: 120m E-W x 50m N-S

No LOS: 220m E-W x 120m N-S

Mortars with TRP

LOS: 140m E-W x 80m N-S

No LOS: same (but the 5% is further out)

Mortars without TRP

LOS: 140m E-W x 80m N-S

No LOS: 250m E-W x 120m N-S

Rockets

Always have about 80% in 200m x 200m circle and about 95% within 300m x 300m, regardless of LOS or TRP.

So, in summary:

Guns and mortars both shoot oval patterns with the long axis E-W. Guns shoot somewhat tighter patterns than mortars. Guns and mortars shooting at a TRP without an LOS gives the same pattern as with an LOS, but the few outside this pattern are further out. However, having neither a TRP nor an LOS greatly increases the size of the pattern. For rockets, none of this matters--you always get the same pattern.

NOTE: this is just how CM handles this stuff. I'm not saying this is realistic

<blockquote>quote:</font><hr>

JD said:

I am less interested in the implications to specific wargames. Like I said above; "As to whether rockets are being accurately portrayed in any wargame, IMHO I think a wargame should reflect a tendency toward much larger dispersion zones for rocket barrages relative to more conventional artillery barrages".

But should the rocket arty get handicapped because of them ?<hr></blockquote>

Of course. It's an historical handicap. Rockets are fired from short tubes or rails, neither of which imposes anywhere near the consistency of trajectory that a gun tube does. Also, rocket motors don't burn as reliably as shell propellant. So it's physically impossible to shoot rockets as accurately as tube arty.

[Radar]

Does anyone know how the dispersal pattern for those Northern Alliance truck mounted rocket artillery? I'm assuming that the mechanics of the weapon system isn't changed much from those used in WWII. :confused:

[Chupacabra]

If they're Katyushas, it's the same thing. A lot of surplus Katyushas wound up in a lot of different places.

During the Angolan civil war, MPLA soldiers realized that two men could carry one Katyusha rocket fairly easily. Make a tripod out of sticks, and you can hit a town with one. You're not going to get any more precise than that, but if the entire town is held by the other side, oh well.

[TigerChow]

One thing that seems to be missed here in the discussion of accuracy of a gun v. a rocket tube - typically, a gun fires its entire salvo from the same tube v. a rocket launcher, which fires its entire salvo from multiple tubes (each rocket having its own tube). Therefore, I would expect more dispersion from a rocket launcher firing from 12 or 16 tubes (or whatever they fire - I'm not professing to be a grog w/ all the answers) than from a single gun firing a 12 or 16 shell salvo.

I don't profess to know what the true dispersion is, just throwing out another possible explanation for more inaccurate rockets.

TigerChow

[Tero]

A weapons dispersion is determined by test firing.

Yes. Finnish artillery test fired every piece to get individual data on each and every gun.

As I recall British Coastal Artillerists were the first folks to start employing something along the lines of firing tables.

Can you say when ?

Surely you are familiar with firing tables.

I am aware of their existence.

I had thought artillerists that rely on “Kentucky-Windage” died away sometime during WWI.

Not exactly. Even today when you are firing over open sights you may not have time or resources to do proper mathematical calculations.

If it is laid out like US ARMY Artillery FM’s there should be a decent write-up on dispersion and exterior ballistics.

I dug it up and it is all there.

One passage states (my translation): "If propable deviation values are known you can in practise calculate hit propability with sufficient accuracy instead of using normal distribution (firing ?) tables. The use of normal distribution density function is more accurate however. The relative difference between standard deviation and propable deviation is

r = 0,675 s.

To calculate the desired hit propability of at least one shot you can calculate the number of required shots with the formula

N = K / hit propability

where

N is the number of required shots "

K is 1.0 for 63%, 2.3 for 90%, 3.0 for 95% and 4.6 for 99%

hit propability is A / 2-SL1Sp where A is the area of the target, SL1 mean deflection deviation and Sp is mean range deviation. The formula is based on normal dispertion and is valid only if the center of impact is at the target and the dimensions of the target are small compared to the mean deviations."

The formula gives the number of shots reguired to hit a 15m by 75 m vessel at 10 km's when the center of impact is at the bow of the vessel and the propable deviations are 1,5v annd 0,5% as 11 shots.

The number of arial rockets required to hit a gun with a 4m vulnerable radius is 126 if the dive angle is 30º, firing distance is 1000 meters and the gun is clearly visible to the pilot. For a 63% hit propability you need 55 rockets.

50% of the rounds fall within the two X’s immediately adjacent to the “O”

And none will fall on the O at all ?

I don’t recall providing my reckoning on numbers of rounds that will hit the MPI.

You did not. Why ?

Your point on bringing this direct fire anecdote up eludes me.

It is not a direct fire anecdote.

The arithmetics is OK but armies did/do include all these deviations into their firing solutions by default.

100% zone for what specific weapon, firing what specific charge, and at what specific range?

Any arty piece, any charge, any range.

Sounds like your talking about a standard sheaf for a mortar platoon?

No, a standard sheaf for any arty battery, or batteries.

I'm talking about systematic error inherent in the fire from one gun.

If the error is systematic how difficult is it to take it into account when calculating firing solutions ?

I am talking about inherent systematic error of one gun firing at a specific range, using a specific charge.

Again, if the error is systematic and all specs are known how difficult is it to take it into account when calculating firing solutions ?

The "aiming" method is very important. It decides if the 50% zones are overlapping or not as it were.

[Tero]

Originally posted by Bullethead:

This is incorrect.

May be. As I said it seems] the fall density and fall patterns are linked to the ordnance caliber. You just do not get the same density with the 155mm as you do with the 75mm, eventhough there is no RL reason for the densities to be different from each other.

This has shown that caliber has no effect on pattern.

IMO the density is what counts, not the pattern as such.

Could you conduct the test with 150/155mm and 75mm respectively ?

However, having neither a TRP nor an LOS greatly increases the size of the pattern.

What about the caliber ?

For rockets, none of this matters--you always get the same pattern.

They are 150 - ~300mm caliber. Would it be an idea to test and compare them against the 14" naval arty (which is of comparable to the larger rockest) ?

NOTE: this is just how CM handles this stuff. I'm not saying this is realistic

Good.

Rockets are fired from short tubes or rails, neither of which imposes anywhere near the consistency of trajectory that a gun tube does.

Depends what is included in the "anywhere near" in consistency.

I am sure some of the inherent inaccuracy was downplayed by deliberate "aiming off".

Also, rocket motors don't burn as reliably as shell propellant.

But any deviation or quality flaws in the shell propellant will affect the shell flight more dramatically than a they affect rockets. Statistically speaking.

So it's physically impossible to shoot rockets as accurately as tube arty.

Not really. What you need is consistent quality and constant/predictable variables. The rest is just vector physics, statistics, trigonometry and geometry.

And lets not forget the fact that you can blanket a more wide area in seconds with a batter of rockets than you can with a batter of field guns. If you get the benefit or surprise you can do more damage with the rockets than a regular arty barrage.

[ 11-26-2001: Message edited by: tero ]</p>

[Jeff Duquette]

<blockquote>quote:</font><hr>Tero Said:Any arty piece, any charge, any range.<hr></blockquote>

Interesting. Please elaborate.

[JasonC]

"I don’t recall providing my reckoning on numbers of rounds that will hit the MPI."

"You did not. Why?"

Err, because it is a mathematical point, and thus has dimension zero, and thus has no area, and thus every shot falls at some distance from it, however infinitessimal. It seems to me a rather silly misunderstanding is all that is behind this part of the discussion.

Obviously, if you want to know about "direct hits" you have to define them such that they can occur. Which means specifying the size of the target. Misses from the point of aim smaller than half the size of the target directly hit the target - obviously. But there is no such animal as the "hit probability" for a mathematical point, without specifized size.

As for the idea that rockets can be "just as accurate" as rifled, tube artillery rounds "if you just know enough", that is simply false. You can know as much as you like about the statistics of the fall of shot, and the dispersion is still there.

What seems to me missing from this discussion is the role of accuracy in artillery shooting, and its relative importance or lack thereof, depending on what you are trying to do. To suppress large numbers of troops in the open or destroy large numbers of soft vehicles, you don't care a whit about point accuracy.

The whole idea is to clobber an entire area. A target 1 km on a side is adequately hit by innaccurate rockets. If they all cluster around the aim point, you gain nothing - to get good coverage you'd just have to widen the sheaf to make up for it. Which is what tube artillery does when firing such missions. Putting all the rounds on one point just wastes blast in overkill.

If on the other hand you are trying to destroy a single, small, point target with a minimum number of rounds fired, accuracy is useful. But that is rarely the case, outside of direct fire (which is much better at it). For one thing, because in indirect fire the battery is not actually aiming at the target to begin with.

In CM, we place a point-target on a continuous map exactly where we want it, and then the shells fall in a distribution around that point. That is not what actually happens. The FO has only an approximate sense of where the center of the distribution (the point of aim) is to start with, because he only sees a limited sample of spotting rounds, which are themselves randomly "disturbed" away from the actual point of aim. And he only estimates their distance from his chosen target, typically in 50m to 100m increments.

Greater accuracy than that is not realistically possible with indirect, observed fire. When a spotting round lands 100m beyond the target, it could have been because it landed in the left far quadrant of the oval of the firing gun's dispersion pattern, and the point of aim is already quite close. Or it could be because the point of aim is 200 meters too long, and the particular spotting round landed 100m short. The spotter may think it actually landed 50m beyond the target, or 200m - all he sees is that the plume doesn't conceal the target from his view. And of course, the line of sight to the target (where the FO's "side to side" error is smallest) is not the same line as the line of fire from gun to target (where the gun's "side to side" error is smallest).

There is not one dispersion pattern involved, in other words. There are at least four. The individual gun's, the sampling error created by a few samples from the gun's (difference between battery aim point and fall of spotting rounds), and an additional statistical dispersion from the FO's merely estimated "sensing" of the location of the shots, and last small variations in where each gun in the battery is pointing, which can easily differ by a single "mil" (1/6400 of a circle), which can add ~10m of dispersion in both angle and distance. All of those variations from a single direction just "add up" statistically into a wider fall of shot around the *intended* aim point.

[Jeff Duquette]

<blockquote>quote:</font><hr>Err, because it is a mathematical point, and thus has dimension zero, and thus has no area, and thus every shot falls at some distance from it, however infinitessimal.<hr></blockquote>

I had considered mentioning this earlier, but thought it might be interesting to see where he went with this.

[Iron Chef Sakai]

you have to fire them en mass, like the germans actualy did, they fired more then a volley lasting 60 seconds. the russian katyusha's were not laser guided either, but when fireing them for an hour or so, the area is going ot be blanketed. don't expect to destroy your enemy with on measly neblewerfer volley, the wepon was not inbtended to be effective deployed like that. i find the games stats to be pretty much as close as your going ot get with vehicles and weapons, and am finding more often then not, the main problem is players deploying the weapons wrong.

[JasonC]

Here is an example of a CM nebelwerfer barrage, used as they were intended. The target was a green US rifle battalion with various attachments and modifications. The line companies were deployed in a wedge, each in a diamond formation with the weapons platoon the rear corner. In the center of the formation, behind the lead company, there was a road column of trucks and jeeps carrying the recon platoon, MG platoon with attached jeep MGs added, ATG platoon, and a platoon of engineers attached. Off the road to the left was the battalion mortar platoon, and off the road to the right was an HQ position with trucks, jeeps. The total frontage was around 1400 yards, and the total depth was about half that. There were 22 vehicles in the road column, and 12 more in the mortar and HQ positions off the road. The total manpower, including drivers, was 858 men.

The Germans had 4 regular 150mm rocket FOs, with the ammo for each nudged to 27 rounds. Thus together the salvo would be 108 rounds, which is one "ripple" by a nebelwerfer battalion (6 rounds each of 6 launchers in each of 3 batteries, firing together), and the way they were actually meant to be used. There is a bit of lead time for the rockets to start landing, and some time dispersion from random variations from the FOs. Once the first rocket landing, it was a two minute affair. The targets had about 45 seconds of recovery on the last turn after the barrage, then both sides (hot seat of course) agreed to cease fire and I examined the results.

The US force lost 89 men including 19 KIA, which was slightly over 10% of the force. In addition, 21 out of 34 soft vehicles were knocked out, including about a dozen burning. 2/3rds of the road column was knocked out, and the road completely impassable due to burning vehicles. One 57mm ATG was dismounted in the roadway. 3/4 of the vehicles of the HQ section were also knocked out, but the 81mm mortar position was spared.

The flank companies were mostly alright, though one platoon lost 7 men and another lost a bazooka. The center company was slightly harder hit. But the largest losses happened in the column, with the recon platoon (at the point of it, which was an aim point of 2 of the 4 FOs) cut in half. Broken drivers were scattered here and there, pinned MGs crawled about, a few HQs were eliminated and others reduced to 1 man, the engineers lost 1 FT and a couple of zooks were gone as well.

A spoiling barrage like that would not KO the battalion fired upon, but it certainly inflicted attrition losses and disorganized the unit. In this particular case, the loss of vehicles was also important, and realistically would have stopped the column for the day - though the infantry might have advanced without their heavy weapons for a klick or two.

In addition, each rocket fired inflicted on average 5/6ths of 1 casualty. Now, the Germans were making and using 1-2 *million* 150mm rockets each year (1 million in 42 and 43, 2 million in 44). Anything like that rate of attrition per rocket fired would mean truly important levels of overall losses. If they got targets of the right density and size, accuracy was irrelevant. They could just keep chucking the things and rack up wounded enemies.

Since some targets were thinner or smaller, some misidentified, some missions harassment or at targets that had already moved, or were dug in, etc, the actual losses per rocket fired were considerably lower in the real deal than in the above CM test shoot. What it shows is that the level of effectiveness they can have in CM, used on the right target, if it had actually been achieved historically would have made the German shooters very happy.

The impression of uselessness comes simply from trying to use a weapon meant to shoot at battalions, against single platoons. And from trying to use 25 rounds instead of 100. A salvo of 100 rockets costs in CM about what a US 105mm battery with the same number of shells costs. The 150mm rockets have twice the blast and arrive in under 2 minutes of firing, instead of 8.

As long as the target is large enough, they therefore give considerably more bang for the buck than US 105mm batteries. But they do not do tight targets, one platoon at a time. If you aren't going to dump an industrial load of HE onto a large target covering a wide area, they are simply not the right weapon for the job. But if you are, they will do it well, and cheaply.

Which after all was the real historical point of the things...

[Bullethead]

tero said:

<blockquote>quote:</font><hr>As I said it seems] the fall density and fall patterns are linked to the ordnance caliber. You just do not get the same density with the 155mm as you do with the 75mm, eventhough there is no RL reason for the densities to be different from each other.<hr></blockquote>

In CM, you get exactly the same density with all types of gun arty, regardless of caliber. They all shoot exactly the same number of shells into an area of the same size and shape under the same conditions. There is no difference at all.

Granted, smaller calibers LOOK like they shoot less-dense patterns. However, this is merely a result of their crater graphics being smaller, so there is more space between them on the map. But in a given AREA, there will still be the same number of craters of whatever size gun you choose.

<blockquote>quote:</font><hr>IMO the density is what counts, not the pattern as such. Could you conduct the test with 150/155mm and 75mm respectively ?<hr></blockquote>

See above. Pattern size, shape, and density are the same regardless of caliber. I've tested it with all calibers of all nationalities. It doesn't matter if you shoot 75mm, 25pdr, 105mm, 155mm, or even 14", you get the same result in CM.

This of course does NOT mean that all these weapons will give you the same net result on a target. After all, the bigger shells are more have a higher CM blast rating and wider kill radii per shell. So the distribution of "firepower" throughout the impact area is different in each case. For instance, a 75mm shell's kill radius in CM is usually less than the spacing of impacts within the pattern area, so targets within the pattern might emerge unscathed. OTOH, a 14" shell's kill radius WAY larger than the impact pattern, making multiple impacts within less than 100m of each other totally superfluous.

This is an area where CM could use some improvement, IMHO. I think the larger weapons should have wider patterns so that less of their firepower is wasted as overkill by the overlapping of their kill radii so much.

<blockquote>quote:</font><hr>However, having neither a TRP nor an LOS greatly increases the size of the pattern.

What about the caliber ?<hr></blockquote>

As I've said before, caliber has NO EFFECT on the size and shape of the impact pattern in CM.

<blockquote>quote:</font><hr>For rockets, none of this matters--you always get the same pattern.

They are 150 - ~300mm caliber. Would it be an idea to test and compare them against the 14" naval arty (which is of comparable to the larger rockest) ?<hr></blockquote>

As I have repeatedly said, caliber has NO EFFECT in CM on the size of the pattern. If you're shooting a gun, you get "Pattern A", regardless of the size of the gun. If you're shooting a mortar, you get "Pattern B", regardless of the size of the mortar. And if you're shooting a rocket, you get "Pattern C", regardless of the size of the rocket.

And BTW, the 14" shell had considerably more explosive content than the largest rockets.

<blockquote>quote:</font><hr>Rockets are fired from short tubes or rails, neither of which imposes anywhere near the consistency of trajectory that a gun tube does.

Depends what is included in the "anywhere near" in consistency.

I am sure some of the inherent inaccuracy was downplayed by deliberate "aiming off".<hr></blockquote>

There is no way to compensate for random inaccuracies, which is what rockets have. Instead of being a tight fit like a shell in a gun barrel, rockets rattled around as they moved down their launcher like a roundshot in an old cannon, so left the launcher pointing only in the general direction of the target. A degree or 2 off at launch corresponds to dozens of meters off at the target. And the shortness of the launch tube or rail gave it less chance to minimize this effect. Which is why rockets have to have multiple launchers and/or submunition warheads to be effective--you need to shotgun the target area because they can't hit a point target.

<blockquote>quote:</font><hr>But any deviation or quality flaws in the shell propellant will affect the shell flight more dramatically than a they affect rockets. Statistically speaking.<hr></blockquote>

Nope. First, regardless of quality, it's easier to obtain consistent burn conditions in a gun tube than a rocket. Second, shell propellant can ONLY affect a shell's velocity, whereas imperfections in a rocket can affect both velocity and direction. Third, because arty is usually adjusted by an FO, any problems with the propellant will be taken into account before FFE begins. Rockets, OTOH, usually didn't have this opportunity--they just unloaded without prior adjustment. Nor would it have mattered if they had adjusted first, due to the other inherent sources of inaccuracy (launcher design and possible change in direction due to bad propellant)

<blockquote>quote:</font><hr>So it's physically impossible to shoot rockets as accurately as tube arty.

Not really. What you need is consistent quality and constant/predictable variables. The rest is just vector physics, statistics, trigonometry and geometry.<hr></blockquote>

Yes really. There is no way to eliminate the inherent inaccuracies in rocketry to the same extent that you can in arty.

<blockquote>quote:</font><hr>And lets not forget the fact that you can blanket a more wide area in seconds with a batter of rockets than you can with a batter of field guns. If you get the benefit or surprise you can do more damage with the rockets than a regular arty barrage.<hr></blockquote>

A given number of rocket launchers can put more HE on a wider area in less time than the same number of guns. However, that's only for the 1st salvo. The guns catch up by sustained fire while the rocket launchers are reloading or, more likely, displacing to avoid counterbattery due to everybody knowing where they are now.

There is no surprise of targets involved with rockets. I've had them shot at me and can attest . Rocket launches in the day make HUGE clouds and trails of smoke and at night make bright flames in the sky. Incoming rockets also make much more noise for a longer time than shells do. All these factors give personnel at the target more time to react than they get with shells. Then you just have to duck for the 1 big impact because, unless multiple rocket batteries are firing in sequence, there won't be any more for some time. With arty, you never know when they'll stop shooting so need to say in cover longer.

Plus, the rocket fire will be over a wide area, without fail. Arty can be fired in a variety of patterns. It could be you want all your firepower delivered more or less to the same point. You can do this with arty but you can't with rockets.

[Tero]

Originally posted by Jeff Duquette:

Interesting. Please elaborate.

I'll try.

The specs on each caliber and gun are known.

The barrel wear is known and monitored for each and every piece.

The effect of athmospherics is known and monitored .

The specs on specific charges are known and monitored. If a batch of propellant is known to be of outright uneven quality or of suspect quality it is known. Assuming of course proper storage at the front lines is and can be observed.

Specific range to target you know, questimate or find out with ranging shots.

The burn time of the propellant and any systematic deviations in it you know to get the shell flight time right. The shell flight time is known. Flight path deviation due to rotation of the shell in flight can be calculated in. Prevailing athmospherics you know (duh ! )

The shell fall pattern with which you hit the target point itself is determined by the firing method: all guns pointing at the target (each gun use a different bearing and the lines of fire intersect at the target point), guns pointing at the target point by the section (each gun in the section points use the same bearing and the lines of fire of the sections intersect), all guns in the battery pointing at the target zone using the same bearing (lines of fire of the individual guns of the battery do not intersect).

The deviation between the target point elevation in relation to the barrel horizontal line is known and calculated in. This is known in Finnish as maastoviiva (terrain line) and maastokulma (terrain angle). I must point out that the WWII Finnish arty had developed this aspect further than most artillery arms by developing before the war a special camera for terrain elevation survey. The camera took two photos simultaneously, one from the terrain below and one from the horizon. Flying altitude was printed on the photo to get the terrain elevations in line with recce/survey photos from adjoining areas. This procedure is often remarked in sources as the entire country being preplotted. Not exactly true but IRL any "unknown" potential combat terrain could be mapped and surveyed for arty purposes within 48 hours, or faster depending on how up to speed the cartography service was. If there were existing recon/survey photos of the area the work went faster. An interesting detail: all existing cameras were ordered destroyed by the Soviets as a part of the peace treaty in 1944. Only one camera survives today.

Questions ?

[Tero]

Originally posted by JasonC:

Err, because it is a mathematical point, and thus has dimension zero, and thus has no area, and thus every shot falls at some distance from it, however infinitessimal.

Well, in the metaphysical level even the shell impact point is a zero dimension entity with no area.

Besides, the O's in his example represent lines of zero width but X meters lenght. The MPI is the intersection of these lines.

Being a mathematical calculation the MPI can be said to be the origo in hex grid of the equation.

Surely it can be calculated how many instances hit grid reference 0.0.

Obviously, if you want to know about "direct hits" you have to define them such that they can occur. Which means specifying the size of the target. Misses from the point of aim smaller than half the size of the target directly hit the target - obviously. But there is no such animal as the "hit probability" for a mathematical point, without specifized size.

I have never heard of an area target that was 0x0 meters.

As for the idea that rockets can be "just as accurate" as rifled, tube artillery rounds "if you just know enough", that is simply false. You can know as much as you like about the statistics of the fall of shot, and the dispersion is still there.

Are you sure ?

Of course the dispersion is still there. Even I would pick a cannon over a rocket when trying to take out a single tank woth stitch fire from a single tube.

But since it is field artillery we are discussing here and the area of the target is xxx meters by yyy meters and most errors are systematic there is no reason why a battery of rockets can not be made to hit the same target as a battery of howitzers. Sure, you can call howitzer fire on a point target more readily and more accurately. But there is absolutely no reason why a rocket battery can not be made to hit a wider target area just as accurately as a regular arty battery.

The whole idea is to clobber an entire area. A target 1 km on a side is adequately hit by innaccurate rockets.

Does anybody actually know which firing method the rocket artillery used in WWII: all mounts pointing at the target (each mount use a different bearing and the lines of fire intersect at the target point), mounts pointing at the target point by the section (each mount in the section points use the same bearing and the lines of fire of the sections intersect), all mounts in the battery pointing at the target zone using the same bearing (lines of fire of the individual mounts of the battery do not intersect). ?

If they all cluster around the aim point, you gain nothing - to get good coverage you'd just have to widen the sheaf to make up for it. Which is what tube artillery does when firing such missions. Putting all the rounds on one point just wastes blast in overkill.

Not in the überFinnish experience. In the summer of 1944 short, powerful, ACCURATE hits at point targets broke off many Red Army assaults when they were assembling. Spreading the fire around the landscape was a waste of resources.

For one thing, because in indirect fire the battery is not actually aiming at the target to begin with.

Where is it aiming then ?

In CM, we place a point-target on a continuous map exactly where we want it, and then the shells fall in a distribution around that point.

This is why I aim the fire off deliberately.

That is not what actually happens. The FO has only an approximate sense of where the center of the distribution (the point of aim) is to start with, because he only sees a limited sample of spotting rounds, which are themselves randomly "disturbed" away from the actual point of aim. And he only estimates their distance from his chosen target, typically in 50m to 100m increments.

Are you discussing RL or CM here ?

Greater accuracy than that is not realistically possible with indirect, observed fire.

Not true. The increment is usually 50 meters. But you can use smaller increments if need be. The gun laying appartuses are graduated so that this is possible.

When a spotting round lands 100m beyond the target, it could have been because it landed in the left far quadrant of the oval of the firing gun's dispersion pattern, and the point of aim is already quite close.

This is why you need to see spotting rounds fired by the entire battery, not just a single gun. When the entire battery fires the FO can see the dispersion pattern as well as the fall pattern and adjust the fire by the battery, not by the gun (which you can also do).

Or it could be because the point of aim is 200 meters too long, and the particular spotting round landed 100m short.

Highly unlikely. Possible human errors mostly associated with poorer quality crews that can cause errors of this magnitude include gun layer error in reading the dial, calculation error at the conversion table. Successive shots will reveal this. If the spotting rounds were from an entire battery and a single shot went this wild off the battery pattern then the human error is the most likely suspect.

What you do is this: first you get the grouping for the whole battery as tight as possible and then all the guns are directed in unison. If care is taken the battery shot grouping should be tight to begin with.

The spotter may think it actually landed 50m beyond the target, or 200m - all he sees is that the plume doesn't conceal the target from his view.

Then he should not be an FO. Or he needs new glasses. Perfect spatial vision is one of of the prequisites an FO has to pass before becoming one.

And of course, the line of sight to the target (where the FO's "side to side" error is smallest) is not the same line as the line of fire from gun to target (where the gun's "side to side" error is smallest).

This is not a serious obstacle. If the army employing the FO knew its trade then the difference in the angles should be already taken into account.

The individual gun's, the sampling error created by a few samples from the gun's (difference between battery aim point and fall of spotting rounds),

The individual guns are all rated for accuracy. When the firing solution is calculated individual characteristics are calculated in. Systematic sampling errors should not occur if the gun log book is up to date.

and an additional statistical dispersion from the FO's merely estimated "sensing" of the location of the shots,

They do get training in it.

and last small variations in where each gun in the battery is pointing, which can easily differ by a single "mil" (1/6400 of a circle), which can add ~10m of dispersion in both angle and distance.

Again, parring gun layer error, if this kind of error creeps in the battery site preparation has been sloppy.

All of those variations from a single direction just "add up" statistically into a wider fall of shot around the *intended* aim point.

Which is what you try to minimize with careful preparations.

[Tero]

Originally posted by Bullethead:

There is no way to compensate for random inaccuracies, which is what rockets have.

Increased weight of fire is one compensatory measure.

A degree or 2 off at launch corresponds to dozens of meters off at the target.

I doubt the tubes or rails allowed full degree deviations.

And the shortness of the launch tube or rail gave it less chance to minimize this effect.

IIRC the Nebelwerfer tube was as long as the round itself. The Katyusha rail is a few times the lenghth of the rocket. The Katyusha was also fin stabilized while the Nebelwerfer was not (IIRC).

Which is why rockets have to have multiple launchers and/or submunition warheads to be effective--you need to shotgun the target area because they can't hit a point target.

They are area weapons by design.

Nope. First, regardless of quality, it's easier to obtain consistent burn conditions in a gun tube than a rocket.

Not if the propellant itself is defective.

Second, shell propellant can ONLY affect a shell's velocity, whereas imperfections in a rocket can affect both velocity and direction.

True. But as I said the deviation in tube arty is more dramatic statistically speaking.

Third, because arty is usually adjusted by an FO, any problems with the propellant will be taken into account before FFE begins.

True.

Yes really. There is no way to eliminate the inherent inaccuracies in rocketry to the same extent that you can in arty.

Only if you are fire single rockets at point targets. When firing at area targets with sufficient amount of rockets the same basic rules apply to both tube arty and rockets.

There is no surprise of targets involved with rockets.

When the first rocket impacts you need to be in cover as they all will land within seconds in the general area.

Rocket launches in the day make HUGE clouds and trails of smoke

Which model where you subjected to ?

and at night make bright flames in the sky.

Then again so does regular arty. If the rocket propellant burns out in the tube then there is less flames in the sky. Also, if the terrain is not open steppes or desert then the horizon will mask most of the smoke and flames anyway.

Incoming rockets also make much more noise for a longer time than shells do.

How much longer ?

All these factors give personnel at the target more time to react than they get with shells. Then you just have to duck for the 1 big impact because, unless multiple rocket batteries are firing in sequence, there won't be any more for some time.

ÜberFinns at least disliked the Stalins Organs because they all impacted virtually simultaneously. They were less dangerous than regualr arty if you were in cover. And when used they were almost invariably used in greater numbers than the guys in the receiving end would have cared for.

With arty, you never know when they'll stop shooting so need to say in cover longer.

IIRC the Red Army used ploys like switching from regular arty to Katyushas (or vice versa) when their infantry was getting nearer the enemy positions so the enemy would keep their heads down that much longer.

Plus, the rocket fire will be over a wide area, without fail. Arty can be fired in a variety of patterns. It could be you want all your firepower delivered more or less to the same point. You can do this with arty but you can't with rockets.

I am not convinced. The rocket launchers can be pointed the same way a regular arty piece can. They can use the same firing methods the regular arty. To me it seems it is only a matter of dispersion and density and how you want to deploy it. Warts and all.

[Tero]

Originally posted by Jeff Duquette:

I had considered mentioning this earlier, but thought it might be interesting to see where he went with this.

Yeah, right.

I then would have been on your case for getting all those X's on the zero width lines of Y meters lenght but not getting an X on the O. Let alone on the intersection of these two infinitely thin but long lines.

[ 11-27-2001: Message edited by: tero ]</p>

[Tero]

A neat little coastal artillery game I found at

http://www.susi.ysakk.fi/~aolpekmu/Coastgun/coastgun.htm

[mensch]

I like Rickets! *foosh foosh*

[JasonC]

You have several problems tero. First you want to make out every variable of the firing process to be deterministic and forecast. Then you need to bring in a backdoor concession, downplayed as much as possible, that actually the targeted area has to be larger for rockets. You try not to notice that the two contradict each other.

The reality is that every term effecting the firing has not only a value but an error bar. The pretended value is really just a mean or expectation. The error bars are the practical reality. Each factor winds up more or less normally distributed about the mean expectation. The size of all the error bars multiplies out to one overall error bar, which is far larger than the bar for the ballistic properties of the gun system alone, since that is not the only factor with error involved.

No, you cannot reduce all of these error bars to nothing by knowing things beforehand. Each shot in actually different from all of the others, and where is lands is not deterministic beyond the placement of the error bars. As for the confusion about what the battery is really pointing at, it is really pointing at an *actual* aim point, which is distributed somewhere around the *intended* aim point because of the error bars of the FO and the spotting rounds. As for the idea that there never is any significant difference between those, tell it to men who lost limbs to friendly fire.

And the ballistic properties of the rockets themselves are far less accurate than tube artillery shells, as the original figures showed clearly enough. "They are pointed in the same way" does not remove a lick of that extra dispersion. It occurs due to random variations in the actual flight of each rocket, as each wobbles about its fins, tosses this way and that, has a motor that burns for a slightly different length of time, facing in slightly different directions over the course of the burn due to the aforementioned wobble, etc.

And you are wrong that accuracy (well below 50-100m that is) is the be-all of indirect artillery fire to begin with. If the target is of an appropriate size (a battalion, a regiment, a division), the accuracy only has to exceed a threshold level, and all of the rest can be accomplished just by dumping in enough rounds and letting the random spread of the fall of shot do the rest. Missing a 10m grid square doesn't mean diddly when you are aiming at a battalion deployed over a square kilometer, and are throwing total numbers of shells with 3 or 4 digits.

Which is what rockets were meant to do, and did. The idea that they are ineffective in CM is due entirely to people expecting to hit single platoons with them. Which would be a waste, because most of the blast thrown would do nothing. But it is equally true that the tightest sheaf and most accurate fire is a waste against large targets, because most of the blast again does nothing, because the center-point of the barrage is already dead.

Did people sometimes use concentrations with that in view in the real deal? Of course. US field artillery sometimes fired 200 guns at a single spot in time on target shoots. From wide angles, up to a full semicircle (which results in a circular impact of overlapping "long-short" lines). But what were the targets of such industrial strength shoots? Not a platoon position, whole enemy-held villages. Some "point target". They certainly called them that, but they are nothing like what a point target means in CM - a single MG.