402 



a 200 



0.1 2 9 I 2 » 10 2 5 100 2 5 1000 



Charge Weight W in pounds 



Figure 13 - Plot of the Critical Depth Do for Migration 

 near the Bottom of the Sea 



In sea water of depth less than Dq feet, the gas globe should rise during the first recompression if 

 detonation occurs at a distance Z * Z^ above the bottom, where Z2 = 2^2? ^2 is plotted in terms of a 

 larger scale shown at the right. In water of depth greater than £)„, the globe should sink toward the 

 bottom if Z = Z2. For fair accuracy the gas globe should be at least ^R^ below the surface of the spa. 



From Figure 11 It Is seen that migration dovmward can be produced 

 by a free surface only If the charge Is less than 0.2 pound, provided deto- 

 nation occurs at a depth at least as great as 2Ri below the surface. In the 

 absence of more exact calculations, it may reasonably be surmised that the 

 globe from 1 pound or more of TNT or tetryl should migrate upward, however 

 close to the surface It may be formed. 



The effect of the bottom Is more complicated because the tota] hy- 

 drostatic pressure, as Influenced by the depth of the water, enters as a new 

 variable. In order to illustrate more concretely the implications of Figure 

 12, there is plotted on a basis of H'' in Figure 13 the depth of sea water Z>o 

 at which R^/Va - ^ -33; the value of Z when Z = ZR^ in water of this depth is 

 shown, on a different scale, as Z^- 



The formulas for D^ and Z^ are 



D„ 



-"[■f (IH'^*-']. ^,-«-^(!^')' 



w< 



In water shallower than D^, the gas globe should rise if formed at a distance 

 Zj or greater above the bottom; in water deeper than Dp, it should sink when 

 it is formed at a distance equal to Z^, and also at progressively greater dis- 

 tances as the depth of water is increased. 



Unfortunately the approximate formulas become unreliable at those 

 short distances which are of greatest practical Interest; they should be 

 fairly accurate if Z ^ 2^2. 



