WEINSTEIN: EXPLOSIVE SOUND SOURCE STANDARDS 



However, when using very shallow charges, I think you have a serious 

 source-level definition problem because you generate a directional 

 pressure field that is highly sensitive to the exact firing depth. 

 You no longer are really using the total charge output, so you no longer 

 have the kind of source levels we are talking about. The best mechanical 

 way of eliminating the bubble that I have heard about is a sort of iron 

 maiden with a Swiss cheese skirt. You simply put the charge down into a 

 big sphere with holes in it and this breaks up the bubble as it forms. 



As far as eliminating the bubble pulse problem by varying your 

 detonation rate in an explosive composition, I think the best you can do 

 is redistribute your available energies somewhat; and you still come up 

 with some sort of oscillation. What you are doing is transforming a 

 solid mass of material into the same volume of gas in a very short time 

 however much you slow down the detonation. Willy nilly, the gas is at a 

 high pressure and temperature, it is going to expand rapidly, and then 

 it is going to collapse. So I really can't see how you could eliminate 

 the bubble pulse. 



Dr. Wyllie: I wasn't talking about eliminating the bubble pulse, 

 but rather the pressure pulse. 



Ms. Christian: Well, in any case, it seems to me you are going to 

 have a double pulse wave, even if you effectively cut off the top of 

 your shock wave and have a slow-rising sinusoidal first pulse. 



We have done a little work along those lines, not very much, using 

 detonating black powder and an ARP propellant. We had problems of 

 reproducibility with those materials. We found, for example, that 

 with black powder you must have a very high containment to make the 

 charge detonate reliably. And with the propellant indeed, you do cut 

 off the top of the shock, but you still have the bubble. So if the 



