ENGINEERING EVALUATION 327 



Umbilical Cord 



No problems were reported with the umbilical cord as assembled at Long Beach Naval 

 Shipyard. Since supporting floats were married to the umbilical cord as it was streamed, han- 

 dling at the test site was cumbersome and time consuming. 



Systems 



Ballast System — In actual operation, certain problems developed in using the system as 

 designed. First, when the end overhead tanks were flooded on surface, trim was difficult to 

 control. These tanks flood independently, and one tends to fill faster than the other. As it 

 does so, that end trims down, increasing the head on the flood valve, accelerating the out-of- 

 trim conditions. Ultimately, the flood valve on the high end broaches and the tank will not fill 

 further. When this happened the tank on the high end was filled by hand from buckets. In the 

 future, provision should be made for better control of flooding of longitudinally flooded tanks. 



A further difficulty was encountered in blowing the center overhead tank prior to surfacing. 

 Sealab was in an inclined position on the bottom, and there was no valve opening on the low edge 

 of the tank. It was therefore impossible to blow all the water out. Some water then had to be 

 blown from the end tanks to remove enough weight to surface. As there was no way of deter- 

 mining the volume of water in any of these tanks when partially full, it was impossible to con- 

 trol trim, and when Sealab II surfaced, it was at about a 30-degree angle. An improved system 

 of blowing tanks is necessary to assure complete removal of water from tanks when desired. 



Electrical System — The electrical system as a whole functioned satisfactorily and intro- 

 duced few problems. The power capacity provided appears adequate on the basis of power 

 consumption during the underwater test phase (see Tables Al, A2, A3, and A4, in Appendix A). 

 The maximum average power requirement was 38.8 kw. There are long intervals between 

 readings during this period, and it appears that some error entered the readings of the watt- 

 hour meter. Since a recording wattmeter was not used, the instantaneous peak-power require- 

 ment is not known and could have been much greater than the maximum average peak load. 

 The average daily power requirement for the 42-3/4-day period was 21 kw. In any case, a 

 maximum of 75kva at unity power factor certainly appears ample. 



The only major problem experienced with the electrical system was with the external 

 lighting. The short life of the 1000-watt incandescent bulbs (rated 50 hours) necessitated fre- 

 quent bulb changing, which proved to be a time-consuming job. The lighting level was not suf- 

 ficient for photography; however, this was not the original intention of the external lighting. 

 Some trouble was experienced by the aquanauts in identifying the proper underwater pigtail 

 connector to be utilized for connecting each exterior light. 



The main complaint concerning the interior electrical system was the location and insuffi- 

 cient number of convenience outlets in the lab area. Also, the level of the interior lighting was 

 not sufficient for photography. Here again, the interior lighting was not designed for this 

 purpose. 



There were no apparent problems with the thermal-magnetic circuit breakers. The high 

 thermal conductivity of helium affects the thermal characteristics of this type of breaker and 

 probably does not provide the proper overload protection for the electrical circuits. The high 

 conductivity of the helium atmosphere also works in favor of electrical equipment, in that they 

 can operate at higher currents without danger of overheating. 



Ventilation System — The ventilation system of Sealab II provided for satisfactory mixing 

 of make-up oxygen, helium, and air. The four dehumidifiers, with a total rated capacity of 

 23.5 gallons of water per day, actually condensed an average of only about three to four gallons 

 per day. The fan motors of the dehumidifiers were replaced by 1/4-hp motors to provide addi- 

 tional load capacity required by the increased density of the Sealab atmosphere. The poor per- 

 formance of the dehumidifiers caused difficulty in controlling the humidity during periods of 

 peak moisture input. Table A4 indicates an average relative humidity of 72.1 percent, but with 

 relatively wide excursions as shown in Fig. A7. 



