View Full Version : K, C, and R.E. factors?
I have a question that I can’t find an answer to. I’ve read the TM’s, FM’s, and other books, as well as searched the web and nothing. I’m hoping someone here will know.
In the breaching formula P = R^3 x K x C. I found that the Navy uses different K and C values than the Army. They also use a much different R.E. factor. Does anyone know why? :confused: At first I though that they all must offset one another and would end with the same solution but they don’t. In one reasonable scenario, R=4, it makes a difference in the solution of 40, just for one charge. The Navy being on the low side.
I’m probably just missing something stupid but I can’t see what that is. Sorry I didn’t include many details. I know you can get this stuff off the shelf but I didn’t want to piss anyone off. If you want the Navy’s reference info to look at PM me, the pdf is available online. I'm not going to link it here for the kids to get.
This isn’t intended to be a HOW TO thread so lets not go there. If this question is out of line please delete it.
Thanks
The Reaper
03-15-2006, 20:37
Not familiar with the Navy formulas, not sure why they are different.
I will say that the Army formula and RE rating have never failed me or my students on a properly constructed and placed charge, but I have only seen a few hundred thousand pounds shot in my career, so I could be wrong.
There could be a fudge factor built in, other than the standard P=Plenty formula.
Once, I saw an 18C use a full M112 charge block to cut a Series 200 padlock from a door. It did remove the lock, and open the door. As well as 10' of wall.
TR
Nuke,
Navy and Army do thing different.. Well, we're on land and they are on water 80% of the time. With that said..
Its all about the science behind it. See the different values are base off who or why the scientist looked at the value in that protocolar value (way). I have seen formulas with different out comes not by the bad math, but by the values that you provide them.
Without looking at what your looking at; this my best way of stating why the K- Factor is different. Is the out come on the "light side". Most likely not, basic CAL PLACE formulas are old and to some out dated. But they get the job done..
Good enough for GOV'T Work as they say.
Look I'm no college professor or something. Just been there, done that and got the T-shirt. To explain the WHY would take to long and I'm not good at it.. the bottom line it is the science behind it.
CAL PLACE formulas can be done at least three different ways. This is because you can do it all the standard way by long division and going to the hundredths. In the six step process. Then you can do it by multiplication almost the same way, Its a value thing again .... and then say with changes in the values or factors.
Now the first two ways you can up in the same basic way with the same answer out come. The last you'll have a different answer but with the same effect, not the amount of explosives at times.
Yes you will or can see different values for RE Factors. As well a better formulas to get better effects with LESS explosives to some degree.
Hopefully this doesn't confuses you more. Which it did ;)
uboat509
03-16-2006, 02:17
I just got out of ANCOC in Feb and apparently everything that I learned in the basic course was wrong. There have been some changes to various formulas including the breaching formulas. Another thing that came out was that several of the RE factors were incorrect owing to some sort of math error that was never corrected. Also it turns out that there are three RE factors for most explosives. There is one for charge to target contact that we use most often, there is one for underwater which, of course, the navy uses most often and there is one for airburst that the airforce uses most often. They gave us a class on how they arrived at these figures with chemistry pressure test and a whole bunch of stuff that the fifty pound brains get and I really didn't (it also didn't help that I am not actually an 18C anymore but they do not have an 18F ANCOC yet).
SFC W
Thanks for the replies. All good info. I looked at all the cases and the Army way is almost always higher. When it's lower it's very close to the Navy's. If my life was depending on it, I'd go with the Army's numbers. I'll have to look around and see if I can find that new work they did to update the formulas. I'm having trouble getting the latest FM but I'm working the proper channels. It probably doesn't even have the new numbers but we'll see.
Again, thanks for the replies.
Just curious...by chance would they be using the metric system of measurement with those formulas?
It was easier to crunch some numbers/do research/make rules, than teach "them" how to use our system of measurement. To make it all work I made my own system of adjust RE factors/rule sets for when using the metric system. That was in the early 90's and I submitted my documentation/research just in case the U.S. ever went with the metric system. Funny thing is I remember being told that we had to learn the metric system because someday the U.S. would soon go to it...that was in the early 70's :munchin
Just curious...by chance would they be using the metric system of measurement with those formulas?
To me P=3/8A is so much better than K=A/38.
Just call me old school, P = R cubed KC always worked for me.
A little too well one time. We had to blow a couple of holes in a wall one time. Me and the junior engineer looked at that wall for a good bit of time through the binos and came up with the perfect plan, charge and placement.
Everything went well until the charges went off. As the dust cleared the TS gave me one of those "D*** S***" looks. The whole building had collapsed. The TS then remarked that it looked like an engineering project and us two bone heads could dig up the cookies we were after.
P for Plenty is not always the best course.
Pete
As a former 12B and 18C if you need to blow something up with precision call in the Air Force!
They got great big bombs and you got a scapegoat!