3. The short-term test to failure at conclusion of 107 pressure cycles 

 caused the capsule to fail at 1,850 psi. The actual implosion pressure of the 

 large-scale capsule matches the implosion pressure of 1,827 psi predicted on 

 the basis of implosion tests on model capsules. Therefore, it can be postulated 

 that no decrease in structural strength occurred as result of the previous pres- 

 sure cycling to which the capsule was submitted. 



Heat transfer capability of the large-scale capsule was established in a 

 stagnant water environment with a 400-watt interior heat source and forced- 

 air circulation generated by a 100-watt interior fan blowing directly on the 

 bottom polar steel plate. 



1 . After thermal equilibrium across the wall of the acrylic plastic 

 capsule was established, the temperature measured on the interior surface 

 of the wall was found to be approximately 3 to 4°F higher than the temper- 

 ature of the water wetting the exterior of the hull. 



2. After establishment of thermal equilibrium, the temperature of 

 the air atmosphere contained within the hull was 12 to 12°F higher than 

 the ambient temperature of the stagnant water wetting the exterior of the 

 hull (Figure 120). 



Tensile strength of joints in the 2-year-old 66-inch acrylic plastic 

 capsule was established at the completion of the pressure test program by 

 cutting tensile specimens from the fragments of the imploded capsule. Sub- 

 sequently these bond test specimens were subjected to uniaxial tensile loading 

 to determine their ultimate tensile strength after exposure to atmospheric 

 environment for 2 years alternating with hydrospace environment while 

 undergoing compressive fatigue testing in the vessel. The tensile strength of 

 the joints bonded with PS-18 adhesive was found to be 9,220 psi maximum, 

 5,680 psi minimum, and 7,350 psi average. When these strength values are 

 compared with the 8,280-psi maximum, 5,150-psi minimum, and 6,700-psi 

 average strength value of PS-18 adhesive (Table 3) measured immediately 

 after casting of a 0.125-inch-thick joint in 2.5-inch-thick acrylic plastic, the 

 following is evident: 



1. A 2-year exposure to atmospheric environment alternating with 

 hydrospace environment in the 0-to-2,400-foot-depth range did not signifi- 

 cantly alter the original strength of the joints. 



2. The 107 pressure cycles in which the typical compressive stress in 

 the joint varied from a minimum of about 600 psi to 1 1 ,000 psi had also no 

 significant effect on the tensile strength of the joints bonded with PS-18 

 adhesive. 



152 



