Chapter 38 

 ENGINEERING EVALUATION OF SEALAB II 



'. B. Culpepper, R. B. Porter, W. P. Frost, and B. Deleman 



U.S. Navy Mine Defense Laboratory 

 Panama City, Florida 



INTRODUCTION 



Project Sealab II was the second in the U.S. Navy series of tests of man's ability to live 

 and work underwater at ambient pressure for extended periods of time. The underwater test 

 phase began Aug. 28, 1965, and was successfully completed Oct. 10, 1965. The test site was 

 approximately 3,000 ft off the Pacific coast at Scripps Institute of Oceanography at La JoUa, 

 California, in 205 ft of water near Scripps Canyon. Twenty-eight men, divided into three teams, 

 lived and worked for 15 days each in a synthetic atmosphere of 4 percent oxygen, 85 percent 

 helium, and 11 percent nitrogen at an ambient pressure of approximately 102 pounds per square 

 inch absolute (psia). 



The Sealab II craft, which served as the undersea quarters for the aquanauts, was 57-1/2 ft 

 long and 12 ft in diameter, with a semielliptic head on either end. It was equipped with the nec- 

 essary life-support equipment, such as breathing-gas systems, ventilating system, heating sys- 

 tem, electric and communication systems, food-stowage and preparation facilities, sanitary 

 facilities, and berthing and work space. 



This report presents a brief description of Sealab II and associated systems and facilities 

 and their evaluation from an engineering standpoint. The evaluation is based on observation, 

 interviews with the aquanauts, and recorded data. 



HULL 



General 



The hull of Sealab II was designed as an internal pressure vessel 12 ft in diameter and 

 57-1/2 ft in overall length, in accordance with the 1962 ASME Boiler and Pressure Vessel 

 Code, Section VIII, unfired pressure vessels. The design working pressure of 125 pounds per 

 square inch gauge (psig) was selected so that the vessel could be fully pressurized on the sur- 

 face and then lowered to the required working depth of 250 ft. Because of handling problems 

 encountered with Sealab I, complete surface pressurization was used to minimize the time re- 

 quired for lowering of Sealab II. The hull-plate material utilized was mild steel one inch thick, 

 since the strength-to-weight ratio was not critical (additional ballast was required for sub- 

 mergence). Some decided advantages in the use of this material for a vessel of this size are 

 ease of fabrication and the avoidance of postwelding heat treatment. The hull ends were ASME 

 semielliptic heads, which were explosively formed because of the long lead time involved in 

 procuring commercially formed heads. For arrangements and locations of items described in 

 the following sections, refer to Figs. 118 through 122. 



Ports 



Eleven circular viewing ports were installed in the hull. To avoid the restricted field of 

 view through the 12 -in. ports in Sealab I, these ports were made 24 in. in diameter. Each port 

 was fitted with an internal pressure-tight steel cover to protect the plastic port lights during 



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