NSWC/WOL TR 76-155 



To determine DTNEG, we plotted the ratio of TFLIGHT (calculated by 



C12) to DTNEG-values measured on the 1973 Chesapeake Bay Program , 



as a function of R /AMAX, where R is the slant range from charae to 



c c 



cavitation closure point and AMAX is the maximum radius of the 

 explosion bubble. This plot is represented by the empirical equation* 



TFLIGHT 



DTNEG = 



4.04 - 1.13 ln(R /AMAX) 



(C13) 



where 



AMAX = 12 .7 



W 



DOB + (33.9/14.7) -PATM. 



V3 



(C14) 



and, AMAX and DOB are in feet, PATM is in pounds per square inch, 

 and W is the explosive weight in pounds pentolite. 



Thus, in summary, when the reflected ray intersected the 

 region of cavitation and Equation Cll was true, Equations C12, 13, 14 

 were used to calculate DTNEG. 



Calculation of DTNEG from Superposition of Direct and 

 Surface-Refelcted Waves . If the reflected ray did not intersect the 

 region of cavitation or Equation Cll was false, DTNEG was calculated 

 from the linear superposition of the direct and reflected pressure 

 waves by means of an empirical equation adjusted to the 1973 

 Chesapeake Bay Test data. This empirical equation was 



*This empirical fit was used to make the kill probability calculations for design- 

 ing the 1975 test program. It has not been re-evaluated using the 1975 test 

 program and other available DTNEG-measurements . 



C-10 



