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 Subject: Digitization and firing table FD    3/22/2007 10:46:24 AM If I can get a CEP reduction from 230m to 75m at the same range, how would that affect the number of rounds I might fire? For example, if I would fire a battery of 8 (105mm) at a target could I reduce the number of rounds to just 2? Any ideas?

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 HIPAR       3/22/2007 12:41:12 PM Let's look at this in a simplified sense ..Consider a target that will be neutralized by one round that falls within 40 meters.  The target is centered within the 75 meter CEP circle.  We fire two rounds.  One (possibly both) of the rounds will fall into the 75 meter circle where it explodes within 37.5 meters of the target; it surely destroys it. Now, if the target is centered in a 230 meter CEP circle and we fire two rounds.  One round will fall anywhere from zero to 115 meters from the target.  The target might not be destroyed; we must fire more rounds to assure one explodes within the required 40 meters.So it would appear that it might be possible to fire just 2 rounds.  BUT, in general, it requires more than 2 rounds for CEP statistics to develop.You must also realize that it requires several rounds to adjust fires and center the CEP circle onto the target before firing for effect. The CEP circle is the shot fall pattern after bias errors are removed.  That's what adjusting fire attempts to accomplish.Guided projectiles are a different story.---  CHAS

 FD       3/22/2007 1:13:21 PM CHAS   Thanks for the reply. I understand and I guess you would have to have some random generating software to see on average how many rounds it would take with a CEP of 75 vs 230. Have you ever seen any fire tables (unclassifed) that might be able to provide me with an answer?

 FD       3/22/2007 1:26:37 PM CHAS   Thanks for the reply. I understand and I guess you would have to have some random generating software to see on average how many rounds it would take with a CEP of 75 vs 230. Have you ever seen any fire tables (unclassifed) that might be able to provide me with an answer?

 HIPAR       3/22/2007 1:43:43 PM I believe you are alluding to the Table of Effects.  I believe this is classified.  The Battery Computer System was classified when the table was in memory. I never needed to see it so I don't know anything else about it.There are ballistics analysts who spend entire careers trying to answer these kinds of questions.  They tend to get 'carried away' with small details.---  CHAS

 FD       3/22/2007 2:01:07 PM CHAS,   How about a more simpler question. What is the CEP of the 105mm at a low angle firing and a high angle firing. I found this for the 155mm "Desired Low angle CEP is 60 Meters. Threshold Low angle CEP is 120 Meters, Desired High Angle CEP is 150 meters, Threshold High Angle CEP is 275 meters. It is further specified that this must be attained at a range of 25,000 meters using a 2hour stale Meterological Message, and unconditiond charges and rounds.". Have you seen anything like this for the 105mm?

 HIPAR       3/22/2007 5:15:30 PM No.  Sorry .. I was more involved with the principles than the actual numbers.The numbers you quoted for 155mm appear to be design goals from the performance specification for a new system.  If you can find the firing tables for your 105mm system, you might be able to learn about the CEP from Probable Error data there.---  CHAS

 Sabre       3/22/2007 5:31:07 PM If I can get a CEP reduction from 230m to 75m at the same range, how would that affect the number of rounds I might fire? For example, if I would fire a battery of 8 (105mm) at a target could I reduce the number of rounds to just 2? Any ideas? Ah, this has been hashed over a coupla times - it depends on your objective (and not just destroy / neutralize / suppress) - a lesser amount of precise munitions might result in the same amount of materiel destroyed, but not have same suppressive effect on the enemy personnel, which can make a big difference.  Consider two scenarios - say, a COLT behind enemy lines trying to take out a truck-mobile SAM battery the night before an attack, and the objective of an infantry company assault the next day.  So in the case of the SAM battery, yes, it's all a game of probabilities and numbers, and a lower CEP should reduce the number of rounds needed to punch holes in the relatively flimsy missiles, radars, and commo equipment.  In the case of the infantry assault, I don't think you would want fewer rounds, even if they are more accurate, since the point of the artillery is to keep their heads down - actually hitting them is just a bonus.  Or think of it this way - a few precise rounds may take out an enemy machinegun, but a constant volume of fire could successfully suppress ALL of the enemy's machineguns, making for a much easier assault. Um, doing some rough calculations (and *not* including anything that is classified) if all you care about is hitting the target and not suppressive effects, then going from 230 down to 75m CEP should allow you to use 1/10th as many rounds (but I probably made a mistake somewhere in my calculations)...

 neutralizer       3/23/2007 5:13:28 AM The first point is that CEP is a very poor measure of dispersion for artillery because PEline is very small and PErange is relatively large, CEP combines the two using RMS, the answer, frankly, is crap if you're looking for something approaching a reasonable model of the fall of shot.   Second point is that PEs in FTs apply to a single gun.  It's very rare that single guns are used.  That leads to the next point that guns don't normaslly all aim at the same point (they can, it's called 'converge').  Historically the guns in a battery have fired with lines of fire parrallel, but for the last 3 or do decades have fired with their aimpoints optimally distributed across the target area.     The next point is the distribtion of the effects themselves.  Forget blast, it's mostly irrelevant.  Bomblets are distributed across an area, but not entirely evenly, and the area of their distribution depends on the HoB and angle of descent, the latter being a function of range and charge (so are PEs, and HoB means there is also a PEheight to worry about).   HE shells rely on fragments for their effect, depending on the shell design and the type of targets that were given to the designers as the important ones.  If men are your target then fragments will be very small, this means they have little of no effect against material, but there will be lots of fragments.  The direction of the main density of these fragments also depends on the angle of descent.   As you've probably worked out by now this is a complicated subject and I've barely scraped the surface.  There's more information on the 'Effects & Weight of Fire' page at  http://members.tripod.com/~nigelef/index.htm .

 FD       3/23/2007 8:14:46 AM Thanks for the good information. So, if all this factors in, why would you want to digitize an artillery system like the 105mm? What benefit would you hope to gain? It appears it would only help in the setup and disperse times and only marginally help with the number of rounds to fire at a target.

 Sabre       3/23/2007 9:25:19 AM Thanks for the good information. So, if all this factors in, why would you want to digitize an artillery system like the 105mm? What benefit would you hope to gain? It appears it would only help in the setup and disperse times and only marginally help with the number of rounds to fire at a target. "Only" help in the setup and disperse times???  Sorry, I had to laugh a little at that one.  Faster occupy and march order (setup and disperse) times are huge advantage in the artillery world!  The most obvious reason is threat of counter-battery fire.  Also, it's all fun and games until you and a couple of tubes are choppered in for an artillery raid to support some attack behind enemy lines, and the only troops available for local defense are any extra gun bunnies or FDC folks you can spare... suddenly you don't want to hang around the gun position any longer than absolutely necessary...
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