42 DESIGN OF THE SEALAB II HABITAT 



Hull Penetrations 



Hull penetrations for all gas lines, water lines, and sanitary drains are located as low on 

 the hull as possible to minimize flooding or atmosphere loss in the event a line may carry 

 away. All penetrations are optimally located so as to minimize length of pipe runs in Sealab n, 

 in particular, high-pressure gas lines. All penetrations are either double- stuff ing tube type 

 or piping direct welded to the hull. A wiring trunk is provided for the benthic lab equipment 

 and outside divers' lights. This trunk is approximately 10 in. I. D. and extends from the hori- 

 zontal centerline of the hull to a point approximately two and one- half feet below the hull bot- 

 tom. A smaller three- inch IPS* trunk is installed concentrically inside the larger trunk to 

 provide for electrical shielding of the divers' lights power cables. The wiring trunk is fitted 

 with a pressure-tight cover which may be easily removed for installation of required cables 

 (see Chapter 9). 



Bilge Drains 



Bilge drains fore and aft are provided for draining bilges to sea while on bottom. These 

 drains are provided with valves for manual operation. 



Ballast Tanks 



The Sealab II is provided with three internal ballast tanks and one external ballast tank. 

 The three internal ballast tanks are arranged fore and aft and shall contain the full length, up- 

 per portion of the hull volume to a maximum depth of three feet. These tanks are designed to 

 withstand a 15-psi minimum pressure differential across the flat bottoms. Each tank is fitted 

 with two vent valves, one at either end, and one flood valve. Limber holes are provided in the 

 internal structure of the tanks to insure complete venting. 



The external ballast tank is approximately eight feet in diameter by seven feet high and 

 located amidship on top of the hull so as to provide a breakwater around the upper access hatch 

 while the craft is on surface. This tank is fitted with one vent valve and one flood valve and is 

 designed to withstand a 15-psi minimum pressure differential. This tank is also fitted with an 

 access hatch in the top to provide surface access to the Sealab 11 interior. 



Ballast System 



A water ballasting system is designed to provide the following characteristics: 



a. Surface Tow 26 tons positive buoyancy 



b. Surface (Prior to lowering) 7 tons positive buoyancy 



c. Lowering (Raising) 4 tons negative buoyancy 



d. On bottom 12 tons negative buoyancy 



This system is designed for surface operation to minimize diving time and is fitted with 

 salvage connections for use in the event of interior flooding. 



Support Structure 



A structure is provided to support the Sealab n hull on the ocean floor. This structure is 

 designed so as to provide approximately six feet of clearance underneath the hull for ease of 

 entry. The base of this structure is designed to provide a maximvmi bottom bearing stress of 

 300 lb/ft at maximum negative buoyancy. 



^Internal Pipe Size 



