(wrenches, drills, etc.) depend upon the sub- 

 mersible's manipulator to apply force either 

 into the bottom or against other surfaces; to 

 do so, the vehicle must be capable of obtain- 

 ing sufficient negative buoyancy to remain 

 stable while the instrument or tool moves. In 

 many cases the submersible cannot obtain 

 sufficient buoyancy and, for example, in- 

 stead of the corer penetrating the bottom, 

 the submersible rises off the bottom by vir- 

 tue of its light weight. The problem is similar 

 to those of outer space and near-weightless- 

 ness and is a serious consideration. In 1967 

 ALUMIJSAUT was frustrated in this way 

 while attempting to collect 3-foot-long sedi- 

 ment cores off St. Croix. When ALUMI- 

 NAUT^s manipulator inserted the hollow cor- 

 ing tube to approximately 10 inches in the 

 sediment, further application of vertical 

 force caused the 76-ton (dry weight) sub- 

 mersible to rise off the bottom. 



Launch/Recovery 



Several instruments have been used from 

 submersibles which are lightweight and 

 bulky (Fig. 11.2). While successful employ- 

 ment may be realized under ideal conditions, 

 the user must consider the impact of foul 

 weather which might move in during the 

 dive and create a surface situation which 

 endangers the instrument during retrieval. 

 DEEP QUEST experienced this situation 

 and, by colliding with the forward bulkhead 

 of TRANSQUESTs stern well, lost a camera 

 to the sea. ALVIN experienced a similar re- 

 trieval problem and lost, but later salvaged, 

 its mechanical arm (5). 



The above considerations concerning scien- 

 tific and engineering instruments on sub- 

 mersibles took many years and many dives 

 to evolve. While many of the problems were 

 anticipated, their frequent occurrence was 

 not. For example, Table 11.1 lists problems 



i 6 ^-^-^-^ :\ 



^ 



Fig 112 Acoustic receiving array on Sr/W ///- (USNUSL) 



541 



