as a fairly accurate relative local positioning 

 reference for search or survey operations. 



Underwater release mechanisms are avail- 

 able which can be operated remotely by 

 acoustic command or set to release on signal 

 from an internal clock or by dissolution of a 

 highly corrodable restraining material {e.g., 

 magnesium). A variety of such devices has 

 been successfully developed for surface oper- 

 ations. The submersible, however, has the 

 distinct advantage of being on-the-scene, and 

 a simple pull-pin release mechanism, such as 

 shown in Figure 10.34, works quite well. 

 Withdrawing either one of the two pull rings 

 will separate the array line from its anchor 

 and allow the transponder or pinger to float 

 to the surface. Sole reliance on mechanical 

 release mechanisms of the pull-pin variety is 

 not recommended for a number of reasons, 

 e.g., vehicle breakdown, homing beacon mal- 

 function and the possible inability of the 

 submersible to return or even find the array. 

 The prudent engineer would do well to con- 

 sider including one of the remote or self- 

 actuating devices as an additional compo- 

 nent of the array. 



The foregoing discussion has been brief 

 and simplistic and is quite different from 

 actual at-sea experience with undersea navi- 

 gation devices. On an individual basis, each 

 pertinent navigation component aboard the 

 submersible and in the homing device may 

 work perfectly in the laboratory, but, when 

 they all must work in concert and in the 

 ocean, the most straight-forward and seem- 

 ingly foolproof concept can become a night- 

 mare of frustration. This is especially true 

 when trying to set up and navigate by a 

 pattern of bottom-mounted transponders or 

 pingers. With the passage of time and a 

 background of thwarted, frustrating efforts, 

 a normally rational human being will, at 

 times, find himself thinking of these inani- 

 mate devices as capricious, mischievous spir- 

 its. In essence, one does not "simply" do 

 anything undersea, and just when the hu- 

 man and non-human components are operat- 

 ing well, the ocean itself may take the oppor- 

 tunity to display its ultimate control. Mr. 

 Robert Worthington, Operations Manager of 

 the DEEP QUEST system, rather nicely de- 

 scribed the problem, "The ideal conditions, 

 although frequently existing in nature, sel- 



dom seem to occur when most desired." The 

 point is: Anticipate the worst and stand by 

 with alternatives. 



MANIPULATORS 



The manipulators on a submersible are the 

 operator's hands and arms, and, in the final 

 analysis, the ultimate manipulator is one 

 that equals dexterity and control of an ac- 

 tual human arm and hand. However, this is a 

 difficult order to fill. H. A. Ballinger (32) 

 aptly described the difficulty: 



"Consider, for example, the seem- 

 ingly simple process of quietly closing 

 a door. The hand proceeds through 

 three dimensions in space to reach 

 and grasp the door knob. It must then 

 describe a true arc, which is parallel 

 to the plane of the floor and centered 

 on the door hinges. As the door ap- 

 proaches closure, the rates of the inte- 

 grated movement must be selectively 

 diminished, and a rotary motion ap- 

 plied to the door knob through a 

 changing axis angle. At the right mo- 

 ment when visual, auditory, and force 

 feed-back confirm, the knob is re- 

 leased. All these actions require a 

 constant feed-back and assessment of 

 data and appropriate motive adjust- 

 ment — quite out of proportion to the 

 apparent simplicity of the operation.^' 



Fig. 10.34 Pull-pin release mechanism. (WHOI) 



519 



