Figure 50. Preparing the two hemispheres for bonding together into a sphere. 



Because of all the problems encountered during the bonding operations, 

 the resulting joints in the 66-inch prototype capsule leave much to be desired 

 and constitute a fruitful area for future improvement. However, one very 

 valuable finding about joints could be expected from hydrostatic testing of 

 the prototype large-scale capsule: Successful, structural integrity of the hull 

 and joints under both operational and proof pressures would serve as proof 

 that the presence of discontinuities (dispersed cavities and separation spaces) 

 in the joints is not a bar to safe operational performance of a spherical acrylic 

 plastic capsule under external hydrostatic loading. On the other hand, if the 

 cavities and separation spaces served as fatigue crack initiators leading to early 

 cyclic fatigue failure, future joints would have to be cast utilizing more refined 

 casting techniques and under tighter quality control to prevent the occurrence 

 of any cavities. 



79 



