Environmental Sensors 



Five environmental factors exert a heavy 

 influence on rescue efforts: Depth, tempera- 

 ture, currents, visibility and sea state. Depth 

 gages are standard on all submersibles, and 

 this value may be relayed to the surface. 

 Should there be no telephone on the vehicle, 

 the support craft may measure the depth. 

 The remaining factors may differ widely 

 from surface values, and must be measured 

 or estimated in situ. Temperature has its 

 greatest influence on divers by both directly 

 and immediately affecting the quality and 

 duration of their performance. The majority 

 of submersibles do not carry an external 

 thermometer, and, hence, have no direct way 

 of measuring seawater temperature. Indi- 

 rectly ambient temperature may be meas- 

 ured by measuring the internal pressure hull 

 temperature which produces an approximate 

 value. The hull material has a major influ- 

 ence on such indirect measurements owing 

 to the different thermal conductivity of met- 

 als and plastics. 



Currents directly affect the maneuvering 

 ability of both manned (including divers) and 

 unmanned devices. Current meters are 

 rarely carried on submersibles; thus, the oc- 

 cupants may only have the ability to meas- 

 ure water speed and direction by the visual 

 observation of suspended particles in the 

 water column. By observing particle move- 

 ment relative to the submersible's heading 

 (determined by a compass) a fairly accurate 

 estimate of direction may be obtained. Speed 

 estimates are far more difficult because 

 there are no reference points; hence, the 

 estimate reduces to "fast" or "slow." 



Visibility ranges are more difficult to 

 measure and no known submersible rou- 

 tinely carries the instruments required for 

 such measurements. There is almost alv/ays 

 a few feet of visibility in the open ocean. In 

 coastal or estuarine areas this is not always 

 the case, and, at times, changing tides, sedi- 

 ment run-off from land and seasonal plank- 

 ton blooms may reduce visibility to nil. 



There is little one can do about high sea 

 states except to wait for better conditions 

 and then act immediately when they arrive. 

 One can recommend that diving only be con- 

 ducted when several days of good weather 

 are predicted, but such recommendations are 



impractical when diving in, for example, the 

 North Sea where "good" weather is a rela- 

 tive term and, at certain times of the year, is 

 measured in hours rather than days. 



Avoidance Sonars 



Submersibles with trainable obstacle 

 avoidance sonars may be able to actively 

 acquire rescuers and direct them to the site 

 by means of the underwater telephone. If the 

 stricken vehicle is immobilized its ability to 

 scan and acquire a target is reduced to its 

 sonar's training ability, and to be effective to 

 its maximum range there must be no obsta- 

 cles to transmission. Such devices can offer 

 significant assistance to rescuers, as was 

 demonstrated when an entangled DEEP 

 QUEST used its CTFM sonar to vector the 

 submersible NEKTON to within visible range 

 (5). 



Such are the capabilities the various sub- 

 mersibles have to avoid, respond to and as- 

 sist in potential or actual emergency situa- 

 tions. It is emphasized that no one submers- 

 ible carries all these devices or possesses all 

 these capabilities. At this point in time, the 

 emergency equipping of a vehicle is up to the 

 owner. 



In September 1972 a Submersible Safety 

 Seminar, sponsored by a variety of govern- 

 ment and private organizations, was held at 

 Ft. Pierce, Florida. The results of this semi- 

 nar have not been formally published, but 

 the proposals for improved submersible 

 search and rescue capabilities offer an in- 

 sight into the thoughts of recognized deep 

 submergence authorities. Though all partici- 

 pants did not unanimously concur with all 

 proposed measures, the following capabilities 

 were listed as desired: 



Submersible: 1. External attachments for 

 providing breathing gas to 

 occupants whenever practi- 

 cal. 



2. A homing device, e.g., pinger, 

 between 10- to 40-kHz fre- 

 quency and 72-hour duration. 



3. Appropriate coloring and op- 

 tical lights for both surfaced 

 and submerged detection. 



4. An appropriate and accessi- 

 ble emergency lift attach- 

 ment. 



683 



