Rocket Artillery to inaccurate?

[Scipio]

I have found a source about the accuracy of rocket artillery:

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

Source is this webpage :

Lexikon der Wehrmacht - Raketenwerfer

Everyone who has ever seen rocket artillery in CM doesn't need a test result here.

Can someone verify this numbers from other sources?

[ 11-22-2001: Message edited by: Scipio ]</p>

[Jeff Duquette]

Probable error is typically expressed in the form of both the range from tube to the Mean Point of Impact (MPI) as well as length and width of the impact zone. The figures you have indicated don’t include range to target.

Typically with conventional artillery probable error increases with increasing range. Rocket Artillery is a bit odd in that probable error does not follow this trend. Rocket Artillery Probable error increases with increasing range to a certain point, than probable error actually begins to decrease slightly. However, based on firing tables I have seen for 28/32 cm rocket projectors the dispersion zone dimensions you pulled from that web-site seem reasonable.

A couple things to bear in mind:

• [1]What was SOP for “danger close” of Rocket fire. Danger Close is sort of an indirect means of telling how accurate or inaccurate a weapon is while firing indirectly. There is a British War Office report indicating the German equivalent of “danger close” for rocket artillery was something like 500 to 600 meters. That’s a pretty good setback distance between freindlies and your potential target. I will find the exact reference if there is an interest.
  
  [2]How does probable error of rocket artillery compare with conventional artillery? Here is an example: US 105mm Howitzer M2A1, Firing shell, HE, M1 (charge 3):
  
  Range = 3000yrd….Deflection Probable Error = 2yrd…Range Probable Error = 18yrd
  Range = 4000yrd….Deflection Probable Error = 2yrd…Range Probable Error = 24yrd
  Range = 5000yrd….Deflection Probable Error = 3yrd…Range Probable Error = 30yrd
  

Probable error for conventional artillery is quite tight relative to rocket artillery.

Obviously all the above is purely systematic error.

[Jeff Duquette]

Hmmm…you changed the intent of your post while I was writing a reply to your original question which I believe was something along the lines of why is rocket artillery so inaccurate in CM…

[Scipio]

<blockquote>quote:</font><hr>Originally posted by Jeff Duquette:

Hmmm…you changed the intent of your post while I was writing a reply to your original question which I believe was something along the lines of why is rocket artillery so inaccurate in CM…<hr></blockquote>

I meant both - the accuracy in CM and the correctness of the source. Maybe CM is correct, but not the source - but I guess that CM is wrong, cause the whole artillery model is false in CM, as already known.

For example - if artillery is off target, it doesn't go in a wider spread, the shells fall with the same spread, but out of the scheduled target zone...

BTS has already announced changes in the artillery system - hope this will be the big changes we need.

[PiggDogg]

Scipio,

I have no facts on which to base my opinion, but I 'feel' (& only feel) that rockets are not too inaccurate in CM. Rocket dispersion feels about right. That is, if they hit anything, it is an accident.

This is sort of like the Brown Bess musket of the Napoleanic era where the saying was to the effect of the following: "A target person was never killed by the Brown Bess user who aiming at him (the target person)". You get the idea.

Cheers, Richard :cool:

[James Crowley]

Neblewerfer missile accuracy in CMBO, or perhaps the spread, is more akin to napoleonic rocket artillery than to that that of a comparatively advanced technology. In other words, bizarrely random.

I have not read a single account anywhere that suggests that this form of artillery was anything other than, at least as accurate as long range mortar fire. Not as tight as traditional arty. but certainly not that far off.

The larger sizes of neblewerfer were generally regarded as somewhat less accurate than their smaller diameter cousins but not, I think, to the extent that CM portrays them.

A shame really, as it makes the weapon virtually useless and totally dependant on a luck hit (and you need to be lucky not to get a hit on your own troops)

[Chupacabra]

I have not seen hard figures on rocket artillery accuracy one way or the other, but it has always felt more or less correct. What I would like to see changed is the manner in which rockets arrive, ie like tube artillery. Please correct me if I'm wrong, but wouldn't rockets pretty much all come down at the same time?

[offtaskagain]

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

I have not seen hard figures on rocket artillery accuracy one way or the other, but it has always felt more or less correct. What I would like to see changed is the manner in which rockets arrive, ie like tube artillery. Please correct me if I'm wrong, but wouldn't rockets pretty much all come down at the same time?<hr></blockquote>

All 36 rockets fired by a standard Werfer battery would land in about 15 seconds. 6 at a time every couple of seconds.

[Jeff Duquette]

I don’t have a lot of game experience with respect to rocket artillery. Everyone I play seems obsessed with playing the Germans. However I am quite content to chug away as the Allied player.

I would tend to agree with Richard Cuccia’s and some of the other folks here in their assessment that rocket artillery in reality is fairly erratic. I think the use of rocket artillery was typically for saturation barrages…drumfire barrage…a poor mans approach to “time on target” for large areal targets. Put the maximum amount of steel on a large target in the minimum amount of time. Accuracy is sacrificed in the interest of rapid saturation.

I think what may be missing in your scenarios Scipio is perhaps the REAL WORLD tendency to employ multiple rocket batteries on the same target. Dispersion isn’t such a huge deal if you have 3 battalions of nebelwerfers all “zeroing-in” on the same target at the same time.

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.

An additional note on “danger close”: As a comparison to German prescribed danger close for rocket artillery (~500m…see my above post) I recall reading in J.Keegan’s “The History of WWI” that the British Army would employ rolling barrages preceding an infantry assault. Setback from an 18-pdr barrage line was prescribed as something like 75m from the assaulting infantry line. This is pretty close especially when considering the fire control standards and communication systems available to FO's\FOO's and FDC's during WWI.

I’m off to eat Turkey. Everyone in the US have a good Thanksgiving. Everyone else in the world have a good day.

[Scipio]

<blockquote>quote:</font><hr>Originally posted by Jeff Duquette:

There is a British War Office report indicating the German equivalent of “danger close” for rocket artillery was something like 500 to 600 meters.<hr></blockquote>

Ehm, if you mean the 'safty zone' - the minimum range or even the minum distance to firendly trrops, this number says nothing about the accuracy. The 'safty zone' for the (modern) German 120mm Mortar was about 500-1000meters - I don't remember exactly, service is 11 years ago - but the dispersion was about 50m - for about 100% of the shells.

My source is speaking about only 50%, so there's already a bigger dispersion included for the other half of the rockets.

[ 11-22-2001: Message edited by: Scipio ]</p>

[Dan Robertson]

Modern spin stablised rockets, like those fired from MLRS have an accuracy of less than 1%.

Firing from 32,000m you would expect a CEP of about 320m. However since each rocket covers a huge area and you fire 12 it is still effective.

The 155m G6 is has an accuracy of 0.37% when using base bleed rounds, so at 40,000m its cep will be 148m.

Both will be improved to about 15m with GPS guided rounds very soon.

WWII artilery rounds are not going to be that far behind modern ones, the only advantage modern ones really have is more precise manufacture.

At 10,000 (typical ranges for most WWII guns like 25pdr) this would result in an accuracy of 40-50m.

Rockets fired from 5000 with modern acuracy would have a CEP of 50m, however WWII rockets are very much less accurate. Even if you watch them go on old news reals you can actually see the dispersion as they fly.

Interestingly as a section if you are calling morter fire you are not meant to call fire on targets less than 800m away, that is to allow for a 200m inacuracy in your own position, a 200m inacuracy in the morters location, a 200m inacuracy in your range to target estimation and finally a 200m miss by the mortor.

These are peace time training guidelines for infantry sections without specialist equiptment. In combat you can call for morter fire wherever the enemy is.

[JunoReactor]

GPS guided shells? Isnt cost a problem?

[Radar]

Na, they shop at Wal-Mart.

[Berlichtingen]

Ok, my only experiece with real rockets are those fired from Cobra gunships... if they hit anywhere near where they are pointed, its an act of God. I suspect that the spread in CM is very close to reality

[gredeker]

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

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

IMHO, cost is a much smaller problem than failing to: make use of existing technology to save friendly lives; increase the efficiency and efficacy of existing inventory; and end conflicts sooner.

Just remember, these are Americans we're talking about. We Americans fight wars just like we do everything else - using lots of resources.

[Jeff Duquette]

<blockquote>quote:</font><hr>Scipio Said: Ehm, if you mean the 'safty zone'<hr></blockquote>

No, Actually I meant exactly what I said. The relatively large Danger Close zone for German Rocket Artillery, as I indicated before, is an indirect indication of the weapons erratic dispersion pattern. I don’t think that even the German Army was particularly keen on fratricide if it could help it. WWII rockets had fairly large dispersal patterns relative to conventional artillery.

Here are the probable error numbers from a TFT for the 28cm Rocket Projector (Schwere Wurfgerat 40):

Range = 600m…Deflection Probable Error = 10m…Range Probable Error = 80m

Range = 800m….Deflection Probable Error = 10m…Range Probable Error = 75m

Range = 1000m…Deflection Probable Error = 15m…Range Probable Error = 75m

Range = 1200m…Deflection Probable Error = 20m…Range Probable Error = 75m

Range = 1400m…Deflection Probable Error = 30m…Range Probable Error = 65m

Range = 1500m…Deflection Probable Error = 30m…Range Probable Error = 60m

Range = 1600m…Deflection Probable Error = 30m…Range Probable Error = 55m

Range = 1800m…Deflection Probable Error = 40m…Range Probable Error = 40m

Range = 1900m…Deflection Probable Error = 45m…Range Probable Error = 45m

Max indicated range is 1925m

So for example at a range of 1500m, and on the basis of a 100 percent rectangle, 50 percent of the rounds will impact within 60 meters (over and short) of the mean range line, 82 percent will impact within 120 meters (over and short), 96 percent will impact within 180-meters (over and short), and 100 percent will impact within 240 meters. In other words your 50% zone is 120m x 60m…82% zone is 240m x 120m….96% zone is 360m x 180m….and the 100% zone is 480m x 240m

Now compare the 28cm Rocket Projector probable errors which is quite large even at 1900m with those of the US 105mm firing HE clear out to 2700m.

Range = 2740m...Deflection Probable Error = 1.83m…Range Probable Error = 16.5m.

The 105mm 50% zone for a range of 2740m is 33m x 3.6m...82% zone is 66m x 7.2m...96% zone is 99m x 10.8m...and the 100% zone is 132m x 14.4m.

For those folks out there that have looked at a few TFT’s in there lifetimes, notice the odd trend for range probable error. It actually decreases with increasing range, and then only at the tail end of the table begins to creep back upward. Deflection error is pretty amazing regarding how large it is even at relatively short ranges. TFT’s I have for Schwere Wurfgerat 41 resemble the trends shown above for the Schwere Wurfgerat 40

[ 11-23-2001: Message edited by: Jeff Duquette ]</p>

[Tero]

Originally posted by Jeff Duquette:

WWII rockets had fairly large dispersal patterns relative to conventional artillery.

In contrast the blast effect radius is wider.

Incidentaly: is there any correlation in CM between the 14" naval arty shell fall pattern and the rocket fall pattern ?

Here are the probable error numbers from a TFT for the 28cm Rocket Projector (Schwere Wurfgerat 40):

Range = 600m…Deflection Probable Error = 10m…Range Probable Error = 80m......

What is the propability percentage of occurrances on these errors ? 50 % ? Or 100 % ? Being "propable" would mean that not all rounds fired go wildly off target. What is the firing sequence turnaround time for a mount ? 1 rocket per second ?

Is there any correlation between a single rocket and a salvo, ie is the target point drifting due to mount deviation caused by recoil ? The normal artillery target rectangle base is 100meters for the whole battery.

I do think the rocket arty in CM gets short changed (along with the rest of the trade). The fall pattern density is too weak and even the zones you describe do not seem to apply.

You say the 50% zone is 120m x 60m. As things stand it would seem that 85% of the rockets fall outside this zone.

[Scipio]

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

You say the 50% zone is 120m x 60m. As things stand it would seem that 85% of the rockets fall outside this zone.<hr></blockquote>

Just to see, I made this test: a 120x80m grain field as target zone, an elite FO with LOS and 150mm Rockets.

Only 1 rocket hits the target zone - this can be seen as coincidence. The rest was spreated over the half map. Must be said anything more?

Would be interesting to see the dispersion of Russian 'Katyusha'. It was a very important weapon on the East Front.

Jeef, excuse the missunderstanding, 'Danger Close Zone' is not in my dictionary (I'm German).

[Phantom Rocker]

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

Ok, my only experiece with real rockets are those fired from Cobra gunships... if they hit anywhere near where they are pointed, its an act of God. I suspect that the spread in CM is very close to reality<hr></blockquote>

We shouldn't compare apples and pears. The Cobra is a helicopter, so targeting unguided weapons is like shooting with a gun from a driving car. And the targets for the unguided missiles are buildings, single positions or even vehicels, so targets of relativ small size compared to the target zone of artillery.

Use the Cobra for area fire into a square of 100x100m, and the most rockets will hit this area.

[ 11-23-2001: Message edited by: Phantom Rocker ]</p>

[Jeff Duquette]

<blockquote>quote:</font><hr>What is the propability percentage of occurrances on these errors ? 50 % ? Or 100 % ? Being "propable" would mean that not all rounds fired go wildly off target.<hr></blockquote>

Tero: I suspect the nomenclature is perhaps different in the Finish Army. You might drop a note to Tommi for exact translation between US ARMY nomenclature and FINISH ARMY info. It will probably be clearer to you via that route. I will try to elaborate a bit here...

Dispersion: If a number of rounds of ammunition of the same caliber, lot, and charge are fired from the same position with identical settings used for deflection and quadrant elevation, the rounds will not all impact on a single point but will fall in a scattered pattern. In discussions of artillery fire, this phenomenon is called dispersion, and the array of bursts on the ground is called the dispersion pattern.

Probable Error: Probable error is nothing more than an error that is exceeded as often as it is not exceeded. Relative to dispersion zones for artillery fire it is an indication of what percentage of rounds fired will fall within a given area. It basically defines a weapons shot pattern based purely on systematic error.

Using the 105mm Howitzer example again if you were to fire 100 rounds of the same caliber, ammunition lot, at charge 3 at a distance of 2700m…50 rounds would fall in an area of 33m x 3.6m. 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. 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.

[Jeff Duquette]

<blockquote>quote:</font><hr>Incidentaly: is there any correlation in CM between the 14" naval arty shell fall pattern and the rocket fall pattern?<hr></blockquote>

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.

<blockquote>quote:</font><hr>You say the 50% zone is 120m x 60m. As things stand it would seem that 85% of the rockets fall outside this zone.<hr></blockquote>

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 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. 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".

I don’t pretend to be an expert on CMBO’s game engine, so I wouldn’t presume to say it models artillery shot patterns well or not so good...at least not without conducting a large number of controlled tests myself. 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.

This really should not be an exercise in mumbo-jumbo. TFT’s exist for just about all artillery ordnance used during WWII so there should be minimal requirements for pulling numbers out of ones ass. The info is all out there for those that have a budget for a bit of research. I would guess that REAL WORLD data on dispersion for different weapon types could easily be plugged into a wargames engine. But than I have never written code for a computer wargame.

[Scipio]

<blockquote>quote:</font><hr>Originally posted by Jeff Duquette:

Even than I suspect I would want to hear what the designers intentions were...<hr></blockquote>

I really would like to hear that, too. About a many aspects. I propose when they are not programming CMBB they spend all their time with answering my questions, instead wasting it with sleeping, eating, family and other secondary things .

[Berlichtingen]

<blockquote>quote:</font><hr>Originally posted by Phantom Rocker:

We shouldn't compare apples and pears. <hr></blockquote>

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

[Scipio]

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

Says who?

[Chupacabra]

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

Says who?<hr></blockquote>

Physics?