PRESSURE HULLS AND 

 EXOSTRUCTURES 



The first consideration in submersible de- 

 sign is to provide the occupants with a dry, 

 pressure-resistant habitat. Secondly, be- 

 cause volume inside this habitat is generally 

 limited, an external structure is required to 

 carry power sources, motors, and other sup- 

 porting systems. Thirdly, to prohibit this 

 supporting structure from entanglement or 

 snagging and minimize hydrodynamic drag, 

 a smooth external covering or fairing is indi- 

 cated. Within these major design considera- 

 tions must be included pressure hull pene- 

 trations to allow occupant entrance/egress 

 and external viewing and penetrations for 

 electrical, hydraulic or mechanical activation 

 and monitoring of external systems. 



PRESSURE HULLS 



SHAPE 



Pressure hull shapes, with few variations, 

 are predominantly spheres or cylinders in 

 various combinations (Table 5.1). A sphere is 

 the most efficient structural form to obtain a 

 minimum weight-to-displacement (W/D) ra- 

 tio, an ellipse is second, and right circular, 

 cylindrical shell reinforced with frames is 

 last. Two types of end closures have been 

 used on cylindrical pressure hulls: A hemi- 

 sphere and an ellipsoid. The most efficient 

 from a strength-weight ratio standpoint is 



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