temperature was in the region of 4,500 to 5,100 juin./in., while those on the 

 exterior were in the 3,500 to 4,100-juin./in. range. The exact magnitude and 

 distribution of strains in the acrylic plastic around the polar plates is not 

 known because they were not instrumented in sufficient detail; there are 

 indications that the ratios of strains at the polar plates to those at the equa- 

 tor were lower than those measured on the model. This was probably caused 

 by the difference in polar plate fastening procedures used for the model and 

 for the 66-inch capsule. While in the model the pretensioned tie rod seated 

 the end plate with only a 100-pound axial force in the 66-inch capsule the 

 polar plate was seated in the polar opening with approximately 100,000- 

 pound force generated by 20 bolts reacting against the split retaining flanges. 

 The very large seating force pretensioned the acrylic plastic around the polar 

 plate to such an extent that only minor compressive strains could appear there 

 during hydrostatic testing. 



2. The strains in the steel bottom plate also varied linearly with 

 pressure. The strains measured on the bottom steel plate varied from one 

 location to another with the strains in one location approaching the yield 

 point of type 316 stainless steel from which the end plates were made. The 

 gage that measured the highest strain on the steel polar plate was rosette 3 

 located on the interior surface of the bottom plate in the immediate vicinity 

 of the plate flange. 



3. When the measured strains at 500-psi short-term pressurization 

 and 68°F were converted into stresses, the magnitude of membrane stresses 

 at the capsule's equator was found to be approximately 3,400 psi on the 

 interior and 2,900 psi on the exterior. The highest measured stress in the 

 steel end plate at rosette 3 was 27,000 psi (Figures 101 and 103). 



Short-term volume decrease, measured with the same type of volume- 

 displacement arrangement as in the model capsules, at 68°F was linear to 

 750 psi, the maximum pressure to which the sphere was pressurized in that 

 test. The volume decrease was approximately 5.5 liters per each 100 psi 

 of short-term pressure increase (Figure 105). When proper scaling factors 

 were applied to the measured volume decrease of the prototype large-scale 

 capsule, it was found to be the same as for the model capsules under short- 

 term loading (Figure 106). Two separate scaling factors were employed. 

 One factor accounts for the fact that the volume of a spherical hull varies 

 as the cube of the radius. The other factor accounts for the fact that the 

 actual wall thickness of the large-scale capsule was somewhat disproportion- 

 ately thicker than that of the model capsule. 



137 



