than that one of the hemispheres or a penetrator failed. The cylinder 

 section was heavily fragmented while the hemispheres were rather 

 recognizable . 



There were no means of estimating whether the structure imploded 

 immediately upon hitting the bottom or remained on the bottom for a 

 time before imploding. In any event, 4,700 feet (1430 meters) is a 

 conservative (or minimum) implosion depth. 



It should be mentioned that the structure was instrumented for 

 strain readings during the implosion test. The damaged penetrator, 

 however, was also the electrical feed- through for strain-gage wires; 

 therefore strain readings were not recorded during the test. 



Discussion of Implosion Strength . The effect of hull stress rate, 

 due to free-fall velocity, was not considered a significant parameter on 

 implosion strength when compared to previously tested cylinder models . 

 For a free-fall velocity of 11.2 ft/sec (3.4 m/sec), the hoop stresses in 

 the hull increased at a rate of 1,900 psi/min (13.1 MPa/min). Previous 

 cylinder models with geometry equivalent to that of the SEACON struc- 

 ture had hoop stress rates about 700 psi/min (9.8 MPa/min). This 

 difference in stress rate would have an insignificant effect on implosion 

 strength . 



Pressure buildup inside the structure was minimal during the 

 entire test. At the 2,900-foot (880-meter) depth it was known that 

 13,000 pounds (5.9 Mg) of seawater leaked to the interior. This filled 

 about one-quarter of the interior volume. By the time implosion 

 occurred, the interior pressure would not have exceeded 5 psi (34 KPa) 

 over atmospheric. The exterior pressure at implosion was 2,100 psi 

 (14.5 MPa). 



The implosion strength of the SEACON hull was 



P. 

 im 



_ 2,100 psi ^ 

 f 10,407 psi ^^ 



37 



