-3- 6X3 



It has oeen suggestea that for a given weight of charge the product of the initial 

 velocity at the centre of the dome ana the fleoth of fletonation Is constants for a 300 ID. weight 

 of charge, a value of v a of 1,500 square feet/seconfl Dasea on results obtainea by Hllliar was 

 usefl to oecide the aeoth of detonation cf 50C lb. A/S bombs. The results cf the oresent anelysfs 

 give variations cf v^3 from 2000 to 6000 with an average of liOOO square feet/socona. There is 

 evidence to support variations J this oraer from tests with mines sc that the assiiootlcn of a 

 constant value does not aopsar to be justlfieo. tt will be seen that t: assume v. a Is constant 

 for a given charge weight Is equivalent to assuming that the maximum oressure in the detonation 

 wave Is constant at a given distance from the charge. Since it Is known that the detonation 

 wave is characterizea by Its maximum oreesure being reached suddenly itr a sHaw froM^ it does 

 not seem lively that the maximum oressure will itself be constant. It would be sxoected to var/ 

 with t'imperature and with manufacturing conditions, and in this regard it fs Intensstlng to note 

 that the variations In the value of v a on individual aays (in table l) are rather smaller than 

 they are in general. 



There is one other point in the analysis to which reference should be made. Within the 

 dome area the surface water is shattered by the suction developed In the reflected wave, but at 

 the boundary, where no soray acaears, it must be assumea that the wdter is caoable of withstanaing 

 the sudaonly ncdled suction. This boundary suction has been calculated in terms of the velocity 

 at the centre of the dome as 



p ^c "s e„ 



2 

 = _ 34 V COS 5 Ib./sq.ln. 

 where is the anglo subtendea by the acme boundary, i.e. 



tan e - ^ 

 '^ 2a 



The values obtained for this suction vary from 700 to i,800 Ib./sq.in. but the greater number 

 are in the neighbourhood of 1,000 Ib./sq.in. 



Conchy signs . 



So far as can be judgea the proooseo metnoa of aeriving the depth of detonation from the 

 distribution of vr-loclty In the dome olves the depth accurately to within a few feet. 



The 'iccuracy obtained can only be oocided with certainty from control tests in which 

 Cepth charges are aetcnatel at known ceoths. 



Sufficient reliance can be cl'.cen on the methoa of analysis to show that the velocity at 

 the centre of the dome is not by Itself a reliable inaication cf the depth. 



