OCEANOGRAPHIC INVESTIGATIONS 363 



crew members be assigned primary tasks associated with particular skills and that responsi- 

 bility for these tasks be at least as important as for diving tasks. It is believed that more ef- 

 ficient accomplishment of work both outside and inside Sealab will result from this approach. 

 Note that this recommendation does not imply discarding the important concept that all crew 

 members be fully trained and responsible for operation and use of all diving gear and all sys- 

 tems which are part of the Sealab. 



It is recommended that effort be devoted toward reducing the acoustic noise level both in- 

 side and outside Sealab. For future work at great depths it would be highly desirable to have 

 Sealab noise levels sufficiently low that ambient noise of biological origin can be measured 

 without undue masking by background noise. 



One or more special-purpose portholes should be provided. One such porthole should be 

 mounted to provide a view of the outside region through which divers enter and leave Sealab, 

 its purpose being to allow determination of whether or not a diver is in trouble. In both Sealab 

 I and II most of the situations in which divers were in real trouble and had critically short time 

 available occurred at or just outside the shark cage. Also, it is nearly unavoidable that divers 

 be occasionally alone in this area for short times. The ability to see such divers from the in- 

 side would be a valuable safety feature. 



Another type of special- purpose porthole is suggested by the fact that the field of view 

 from any porthole in Sealab II was very narrow. To observe adequately the behavior of active 

 animals such as sea lions was not possible because of the narrow, nonoverlapping fields of view 

 from Sealab II. One way to obviate this problem would be to provide a cylindrical glass port 

 of the pillbox type at the top and/or on each side of future Sealabs. Such viewing ports are 

 mechanically simple and rugged, yet provide much larger fields of view. 



It should be noted that the potential of porthole observations for acquisition of scientific 

 data (particularly in biological studies) has not been nearly fully exploited; plans should be 

 made to do so in future Sealabs. It should also be realized, however, that erroneous impres- 

 sions can be gained from porthole observations, particularly as regards water current and 

 motion. For example, in Sealab II it was noted on occasion that water was going down by one 

 port hole and, at the same time, going up by an opposite port hole. This type of flow, typical 

 of that around a cylinder at high Reynolds number, consists of eddy shedding and unsteady 

 movement of the stagnation point around the periphery of the cylinder. By viewing such flow 

 from inside the cylinder it is very difficult to infer accurately details of the outside flow away 

 from the cylinder. It should be possible, however, to place a set of flow and/or pressure sen- 

 sors on a cylinder such as Sealab so that (with appropriate averaging techniques) current speed 

 and direction can be accurately recorded. Consideration should be given to the idea of provid- 

 ing such special oceanographic instrumentation for future Sealabs; this concept is discussed 

 more fully below. 



Turning from Sealab design features, we now discuss results of evaluating Sealab II as an 

 oceanographic platform and make recommendations for future Sealab oceanographic programs. 



In the preliminary proposal for MDL participation in the Sealab II program, it was pointed 

 out that Sealab might well be the long- sought- after stable platform from which to measure 

 waves, currents, and tides and from which to obtain badly needed information on near-bottom 

 features of such scale that the trained and interpreting human eye is needed for decisions about 

 deployment of instruments and correlation of observations. Experience gained through partici- 

 pation in Sealab II yields the conclusion that Sealab platforms do indeed provide the capability 

 to attack effectively these and many other significant oceanographic problems, the solution of 

 which would lead to a better understanding of the marine environment and how to e.xploit it. 

 Sealab II, however, was not specifically designed as an oceanographic platform, and it is obvi- 

 ous that certain modifications, and/or additions (some of which have been discussed in preced- 

 ing sections) would greatly enhance its oceanographic capabilities. A particularly valuable 

 specific addition for future Sealabs would be the inclusion, as an integral part of the design 

 concept, of special oceanographic instrumentation. This instrumentation, although initially 

 expensive, can be designed for adaptation to all future Sealab habitats. Included in this instru- 

 ment array should be sensors for measuring temperature, currents, light level, salinity, sound 

 velocity, ambient noise, pressure fluctuations, tides, bioluminescence, water clarity, and others, 



