Thomm Posted February 13, 2002 Share Posted February 13, 2002 Originally posted by redwolf: First error discovered was that a pure detection on sounds needs at least three (not two) detection points.I can verify this! If you have two mikes (x1,y1) and (x2,y2) and a time=distance difference dr12 then you have three equations r1^2 = (x-x1)^2 + (y-y1)^2 r2^2 = (x-x2)^2 + (y-y2)^2 r2 = r1 + dr12 for the FOUR unknowns x,y,r1,r2 If, however, you have 3 mikes and an additional distance difference dr13 then you have 5 equations r1^2 = (x-x1)^2 + (y-y1)^2 r2^2 = (x-x2)^2 + (y-y2)^2 r3^2 = (x-x3)^2 + (y-y3)^2 r2 = r1 + dr12 r3 = r1 + dr13 for 5 unknowns x,y,r1,r2,r3 Hint: Do NOT try to calculate a closed form solution for the system of equations. It would fill several pages! Regards, Thomm Link to comment Share on other sites More sharing options...
John Kettler Posted February 13, 2002 Share Posted February 13, 2002 Someone asked for configuration data on German multiple rocket projectiles other than the 15cm. Nebelwerfer. I therefore dug out my carefully guarded copy of T.J. Gander's FIELD ROCKET EQUIPMENT OF THE GERMAN ARMY 1939-1945, Almark Publications, London, 1972. Page 24 lists the 21 cm Wurfgrenate Spreng as being conventional in layout, with the exception that the warhead was fitted with a false ogive. The warhead proper weighed 90 lbs., of which 22.4 were TNT. Weight overall was 241.3 lbs., with propellant amounting to 40.25 lbs. Page 27 lists the 28 cm Wurfkorper Spreng as being of conventional layout and weighing 181 lbs., of which 110 lbs. were TNT or Amatol. Whee! This rocket constituted 5/6 of the loadout of a Schweres Wurfrahmen 40, the last rocket being a 32 cm, incendiary of almost identical construction, weighing 174 lbs., but with a warhead of 11 gallons of mixed petrol and Diesel fuel. Propellant was 14 lbs. 9 oz. Page 30 lists the 30 cm rocket as being of conventional layout, weighing 277 pounds, of which 100 lbs. of amatol made up the bursting charge and 33 lbs. were propellant. Hope this helps. Regards, John Kettler Link to comment Share on other sites More sharing options...
Thomm Posted February 13, 2002 Share Posted February 13, 2002 Originally posted by MajorBooBoo: Extra credit: Solve this..My example: Mike1 (-2500, 0) Mike2 ( 0, 0) Mike3 (+2500, 0) Source (+1250,10000) Relative Timing Errors: +0.01 s for Mike2 -0.01 s for Mike3 Yields absolute position error of 178.7 m. Regards, Thomm Link to comment Share on other sites More sharing options...
MajorBooBoo Posted February 13, 2002 Share Posted February 13, 2002 Originally posted by Rollstoy: </font><blockquote>quote:</font><hr /> I can verify this! If you have two mikes (x1,y1) and (x2,y2) and a time=distance difference dr12 then you have three equations r1^2 = (x-x1)^2 + (y-y1)^2 r2^2 = (x-x2)^2 + (y-y2)^2 r2 = r1 + dr12 for the FOUR unknowns x,y,r1,r2 Regards, Thomm</font> Link to comment Share on other sites More sharing options...
Thomm Posted February 13, 2002 Share Posted February 13, 2002 Originally posted by MajorBooBoo: Isnt r2 a known though?Neither r1 nor r2 is known beforehand, only the difference between the two (as long as you rely exclusively on sound measurement). So there is basically no sensible way to know that the sound traveled 1.18 s to the first microphone. For this reason I came up with my own example based on three microphones and (what I hope) realistic distances. Regards, Thomm Link to comment Share on other sites More sharing options...
MajorBooBoo Posted February 13, 2002 Share Posted February 13, 2002 Pardon. i meant dr2. So R2 can be replaced with R1 +404.74? The knowns are: Speed of Sound 1000 meters between recievers. 404.74 time lag from sound (dr2) R1=R2-404.74 (or however you make your R's) exact cartesian coords of recievers Anything else? [ February 13, 2002, 11:37 AM: Message edited by: MajorBooBoo ] Link to comment Share on other sites More sharing options...
Thomm Posted February 13, 2002 Share Posted February 13, 2002 Originally posted by MajorBooBoo: Pardon. i meant dr2. So R2 can be replaced with R1 +404.74?Yes. The third equation does this and is "consumed" in the process. This leaves you with 3 unknowns x,y,r1 and two equations -> and the problem is still not solvable. Math (and grogs) sayz: you need THREE microphones! Regards, Thomm Link to comment Share on other sites More sharing options...
Thomm Posted February 13, 2002 Share Posted February 13, 2002 Originally posted by MajorBooBoo: Anything else?Yes. A third microphone! [ February 13, 2002, 11:48 AM: Message edited by: Rollstoy ] Link to comment Share on other sites More sharing options...
MajorBooBoo Posted February 13, 2002 Share Posted February 13, 2002 Very good. You are sticking to your "guns". No pun intended (what field are you in? again, no pun intended, I am not going to CB your "field") lets say that is right (it is, technically right), how long would it take to solve that equation with 3 mikes? If you had help (no maple programs/calculators or that sort)? Would you go AWOL if you had to do it 8 hours a day? Link to comment Share on other sites More sharing options...
MajorBooBoo Posted February 13, 2002 Share Posted February 13, 2002 Originally posted by John Kettler: Someone asked for configuration data on German multiple rocket projectiles other than the 15cm. Nebelwerfer. I therefore dug out my carefully guarded copy of T.J. Gander's FIELD ROCKET EQUIPMENT OF THE GERMAN ARMY 1939-1945, Almark Publications, London, 1972. ...conventional in layout..Hope this helps. Regards, John KettlerSo most other Nebelwerfers evolved towards a forward mounted HE charge (conventional layout)? Is that correct? I believe these also had inferior accuracy but dont know if thats directly attibuted to mass placement or just the size of the things. The germans did go for more HE thats for sure. What about the russians? Did they develop super katyushas? The germans stuck with the spin stabilization also. Interesting. Link to comment Share on other sites More sharing options...
Asok Posted February 13, 2002 Share Posted February 13, 2002 The following figure demonstrates why two microphones won't do. With only two mikes, you will get an infinite amount of possible gun locations, a line passing X1 and X2 in the figure. You really do need three mikes or some other source of extra info. regards, Asok Link to comment Share on other sites More sharing options...
MajorBooBoo Posted February 13, 2002 Share Posted February 13, 2002 Is this correct? I am not saying it is or it isnt. Does it check? Could sound (just think of the circles emanating from the two seperate source points X1 and X2 in ASOk's diagram (thank you for the visual aid by the way) really have the same time differential? Does a further gun produce a shorter time differential or a greater one? does it depend on the layout? Is it possible the guns could be on some line of possible answers? A curve/spiral of possible answers? I hope to hear from some others also. This is very interesting. Previously I said that theres mirror answers. Can that be true or possibly a clue or just false? Noone should take any offense or get aggravated/irritated. I am demonstrating that maybe NOONE (me too) KNOWS everything about CB here. Even that may not be true. I am fascinated on how the technology of that day could do it and have my suspicions. Link to comment Share on other sites More sharing options...
Chosun-few Posted February 13, 2002 Share Posted February 13, 2002 Love the maths, but have a question.. What happens when 2 batteries fire fron different locations at APPROX the same time, mic 1 hears battery 1 then mic 2 hears battery 2 thinking it is battery 1 then mike 2 hears...etc. Link to comment Share on other sites More sharing options...
Scott B Posted February 13, 2002 Share Posted February 13, 2002 Originally posted by MajorBooBoo: What about the russians? Did they develop super katyushas?They went in two directions - they made larger rockets (up to 310mm, if memory serves) and made launchers that fired more of the smaller rockets (the mid to late war BM-8-48 fired 48 82mm rockets). I don't have production figures or warhead data on me here at work, but I'll have a look when I get home this evening. Scott, who's happy they have radar for CB these days. PS: when are you going to get to shell-crater analysis? Link to comment Share on other sites More sharing options...
MajorBooBoo Posted February 13, 2002 Share Posted February 13, 2002 Originally posted by Chosun-few: Love the maths, but have a question.. What happens when 2 batteries fire fron different locations at APPROX the same time, mic 1 hears battery 1 then mic 2 hears battery 2 thinking it is battery 1 then mike 2 hears...etc.This would be in the benefit of the firer woudln't it? I had previously said that battles became all or nothings and this is the reason. A better tactic would be to time the sound arrival so that IT arrives at the mic line confounding the CB guys. Ripple firing at sporadic mismatches floods the receptors. Rnge would play in though. The energy levels might be discernable and the CB guys could seperate out whos who. If a forward gun can time his firing such that ITS sound arrives at the same time as a rear battery (same calber) on the mics, then HE' is flooding the floor and confounding the CB. He has to haul ass though. Theres more to it than just sound. Frequency plays in big as do other sound engineering principles. Is it the BOOM of the guns discharging explosive or the ringing of the guns barrel thats important? Link to comment Share on other sites More sharing options...
MajorBooBoo Posted February 13, 2002 Share Posted February 13, 2002 Originally posted by Scott B: PS: when are you going to get to shell-crater analysis?http://www.adtdl.army.mil/cgi-bin/atdl.dll/fm/6-121/APPB.PDF Print out and read this. Direction can be obtained from some shell strikes by the way. Link to comment Share on other sites More sharing options...
Scott B Posted February 13, 2002 Share Posted February 13, 2002 Originally posted by MajorBooBoo: </font><blockquote>quote:</font><hr />Originally posted by Scott B: PS: when are you going to get to shell-crater analysis?http://www.adtdl.army.mil/cgi-bin/atdl.dll/fm/6-121/APPB.PDF Print out and read this. Direction can be obtained from some shell strikes by the way.</font> Link to comment Share on other sites More sharing options...
JonS Posted February 13, 2002 Share Posted February 13, 2002 Originally posted by MajorBooBoo: ... how long would it take to solve that equation with 3 mikes? If you had help (no maple programs/calculators or that sort)? ... The RA had a primitive calculator capable of first order DEs. Link to comment Share on other sites More sharing options...
Iron Chef Sakai Posted February 13, 2002 Share Posted February 13, 2002 7 page thread for the neblewerfer?? I think the scientists and engineers who developed the weapons used less space designing then this thread does. If it makes you all feel realy smart to copy already invented and documented information out of books to have a mock scientific debate on facts that have long been concluded and agreed upon then go nuts. Mabe someone here will be scouted by a Nasa employee and offered a postion. Some one throw in some Katyusha material so this thing does'nt get any more stale then it is. I'm not trying to be rude...it's just i think BTS has modeled the Nebelwerfer right and i'm sure it will be fine in CMBB. Link to comment Share on other sites More sharing options...
JonS Posted February 13, 2002 Share Posted February 13, 2002 go away you silly little man. Link to comment Share on other sites More sharing options...
Andreas Posted February 14, 2002 Share Posted February 14, 2002 Originally posted by JonS: go away you silly little man.The Italics are a nice touch. As for the number of mikes - three are really the minimum, based on empirical data (although I still have to have a look at the link Brian kindly provided). The whole system consisted of four-six for a battery, spaced well apart. All this calculating stuff is really not very meaningful in this context unless you look at how the real life system looked like... Link to comment Share on other sites More sharing options...
Redwolf Posted February 14, 2002 Share Posted February 14, 2002 The actual math for the pure-sound counterbattery calculation is complicated enough that I came up with a formula that gives invalid results. I have to defer that to the weekend. Sorry guys. From what I can see, the formular that will be the result will probably be well executable with a (what's the English word for Rechenschieber?) calculater-slider. So that's doable in WW2. Heck, they built a nuclear bomb. Link to comment Share on other sites More sharing options...
MajorBooBoo Posted February 14, 2002 Share Posted February 14, 2002 Originally posted by Iron Chef Sakai: ..realy smart .. Mabe ... I'm not trying to be rude....I hate to say this but this guy actually cracks me up. In a 'Peng' sort of way. Hes just so over the top wacky. Thanks Chef. You made me laugh. Link to comment Share on other sites More sharing options...
Sir Uber General Posted February 14, 2002 Share Posted February 14, 2002 Did either side play around with faked arty sounds to throw off enemy CB? Link to comment Share on other sites More sharing options...
Redwolf Posted February 14, 2002 Share Posted February 14, 2002 Originally posted by Sir Uber General: Did either side play around with faked arty sounds to throw off enemy CB?I figured it would be appropriate to leave this honor to Sakai, who hopefully has a spotwatch when my present arrives. [ February 14, 2002, 12:08 PM: Message edited by: redwolf ] Link to comment Share on other sites More sharing options...
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