DESIGN, CONSTRUCTION, AND OUTFITTING 83 



Arawak or "hookah" system and is very desirable for short sorties in that it frees the swim- 

 mer from cumbersome scuba devices. 



Atmosphere Treatment— In addition to the control of CO 2 and hydrocarbon content, means 

 are provided to regulate the temperature and humidity of the Sealab atmosphere. 



There are thermostatically controlled baseboard convection heaters in each area except 

 the entry. Radiant heaters are provided in the entry area, nonthermostatically controlled. 

 Imbedded in the concrete deck is a mineral insulated (MI) electric cable, with its own independ- 

 ent thermostat control. The maximum total heating load is 25 KW. Normal design tempera- 

 ture is 88°F. 



Eight commercial dehumidifier units are installed, each with a capacity of 47 pints/day to 

 keep the relative humidity at 60 percent. Each is controlled by a humidistat. 



The increased heat transfer characteristics of the helium atmosphere require two inches 

 of standard submarine cork insulation on the hull and one inch on the overhead. 



Direct reading and remote transmitting temperature and humidity sensors are installed. 



Fresh Water and Plumbing Systems — A boosted fresh water supply consisting of two one- 

 inch PVC pipes laid from the shore to Sealab n is the primary source of fresh water. Demand 

 is based on a maximum usage of 10 gal/min at 50 psig. In addition, a line from Sealab n to 

 the staging vessel on the surface provides a means for topping off the staging vessel tanks 

 during periods of low Sealab usage. 



An emergency fresh water tank is installed with a 150-gallon capacity in the overhead of 

 the laboratory area. Also in the laboratory is a 50-gallon hot water tank with a short recovery 

 time. 



The plumbing system consists of one small boat-type water closet, two tub showers, a 

 washbasin and two sinks, one in the galley and one in the laboratory. 



Drainage is designed to be aft towards the entry area where a sump and overboard con- 

 nection are installed. Hoses are installed externally to carry the drains away from Sealab. 

 The water closet has its own salt water flushing and overboard discharge connections. 



Electric Power Distribution — Primary power is led to Sealab n via an underwater 2300- 

 440 V transformer from the La Jolla power system. A 300-ft cable carries 440 v, three-phase 

 60-cycle power into Sealab designed for a maximum of 75 kva. Alternate power is available 

 via a cable in the umbilical. This is also 440 v, three phase, 60 cycle. 



The 440-v supply is used directly for the hot water, baseboard, and deck heaters. 400- 

 120-v and 440 -208-v transformers handle the remainder of the loads. Standard protective dis- 

 tribution panels, circuit breakers and switches are utilized. 



A transfer panel enables transfer from normal to alternate power. 



The Umbilical — The services from the staging vessel are brought down hoses and cables 

 nested in what has become known as the "umbilical." Secondary power via a three -conductor 

 cable, a multichannel communication cable, a gas-supply hose, a gas-sampling hose, and a 

 compressed-air hose for external tool use make up the umbilical. The Sealab terminations 

 for these lines are centrally located at the conning tower. The lines are brought together and 

 lashed in a canvas jacket every few feet to form a nest. The staging vessel terminations are 

 hooked up prior to lowering Sealab. 



Communications Via Umbilical — There is a helium speech unscrambler on the staging 

 vessel modulating and converting the helium distorted speech of the subjects and is fed via one 

 channel with transmitting stations in the laboratory, galley, and berthing spaces in Sealab n. 

 A two-way electrowriter is also installed between Sealab and the staging vessel. Four TV 

 cameras mounted in Sealab n transmit their output to monitors on the staging vessel. In 



