ENGINEERING EVALUATION 331 



Ports — Since viewing ports in the berthing area and in the entry area were not utilized, 

 these ports should be eliminated. The internal pressure-tight covers for the remaining ports 

 should be redesigned for use of a radial squeeze O-ring seal. This change should eliminate 

 the leakage problems and will allow the use of fewer bolts with less torque. 



Another desirable alteration is the design of viewing ports to withstand the required pres- 

 sure differential. This end could be attained by using heavier, high-strength glass or by re- 

 ducing the port diameter, or both. This alteration would eliminate the need for internal covers 

 and for pressure equalization of the volume between the internal cover and the port glass. 

 External covers would still be required for protection during Sealab handling operations. The 

 external protective covers should be hinged to the port frame to reduce handling difficulty and 

 improve diver safety. 



Access Openings — The emergency exit hatch should be made more accessible, possibly to 

 the extent that it may be used as a secondary access hatch for resupply. This provision would 

 relieve the congestion and traffic at the main access hatch. Improved bilge drainage in this 

 area should be provided. 



The surface access should be provided with a counterbalance system for improved ease of 

 opening and closing and a latch for securing when open. This hatch should also be insulated to 

 reduce heat loss and to prevent moisture condensation. 



The main access hatch appears to be adequate without modification. One item to be con- 

 sidered is a means of draining the bilge around the hatch thimble. 



Entry Trunk — As a means of providing much-needed additional space, the entry trunk 

 should be enlarged and enclosed (nonpressure) for use as a diving station. This area should 

 be used for: 



1. Entry and exit. 



2. Storage of diving gear. 



3. Donning and doffing of gear. 



Large viewing windows should be installed in the entry trunk to permit observation of the 

 outside area and divers in the vicinity. These observation windows will eliminate the need for 

 the shark cage. This modification, however, will depend on the following additional design 

 considerations: 



1. Additional life-support requirements, including heat and atmosphere control and 

 circulation. 



2. Increased buoyancy at the stern of the craft. 



3. A water-trapped entry arrangement of adequate displacement volume, which can be 

 negotiated by the divers in full diving dress with a minimum of climbing. 



4. Downward extension of all open-ended hull penetrations to the lowered water level in 

 the entry. 



A similar room at the emergency access hatch would serve for use as a resupply and ob- 

 servation station. This arrangement would offset the increased buoyancy at the stern. 



Support Structure — In order to provide increased versatility in adapting the Sealab to 

 varying bottom conditions, the supporting structure should incorporate a means of self-leveling 

 when placed on the bottom. The operation of this leveling system should be completely auto- 

 matic or require little diver support. One method of accomplishing this objective would be the 

 use of four cross-connected hydraulic rams. When placed on the bottom, hydraulic pressure 

 equalization between pairs of rams would allow the Sealab to trim itself. Stabilization of the 

 system (hull and support or hold-down structure) would re^.uire closing only one valve in each 

 of the two cross-connecting lines. These valves could be operated remotely from inside Sealab. 



