SEARCH FOR THE THRESHER — SPIESS AND MAXWELL 381 



the small area directly to the east of the strip of debris charted by 

 Atlantis 11^ Gillis^ and Conrad. This was the area in which the 

 magnetometer contacts were obtained, as well as the photographs of 

 the larger pieces of debris. Because this area was sufficiently re- 

 stricted in size to allow effective use of Trieste^ the bathyscaphe was 

 brought to the scene. She is one of the few craft in the world (and 

 the only one belonging to the United States) which can operate to 

 the depth necessary for observing the bottom in this area. Like all 

 others (French and Japanese craft), Trieste lacks the cruising range 

 and maneuverability necessary for an extensive search operation, but 

 her observational capability makes her a useful investigative adjunct, 

 once an area of high probability has been established. Operation of 

 this craft is time-consuming and provides a good example, for the 

 nonseagoing scientist, of the slow pace at which many seagoing experi- 

 mental activities must be conducted. Trieste must be towed from port 

 to the operating area at a speed set by the conditions of wind and sea, 

 at best not in excess of 5 knots. She is essentially a fair-weather ve- 

 hicle and is very vulnerable if caught under tow in a storm ; thus, she 

 is not taken out of port unless there is a prediction of good weather for 

 the entire operation period. 



In the present case, the tow from Boston took about 3 days. Once on 

 station, it is necessary to transfer personnel from the towing ship to 

 Trieste in small boats, and to maintain divers in the water until she has 

 started her descent. This portion of the operation typically takes 

 more than an hour. Once on her way, Trieste sinks at a rate of less 

 than 1 meter per second, requiring some 60 minutes to reach bottom in 

 the Thresher area. After Trieste''?, arrival on the bottom (and possi- 

 bly after oscillating maneuvers to free her from mud, if her descent 

 was not checked in time) , her ballast is adjusted and she can begin to 

 cruise horizontally at speeds of % to 1 meter per second at an elevation 

 of about 10 meters above the sea floor. From this position, one of 

 the three men in the sphere (2 meters in diameter) can observe a patch 

 of sea floor a few meters wide and 10 to 15 meters long, ahead of the 

 vehicle. Her turning circle is about 20 meters in diameter, and thus 

 a 180-degree turn takes about 2 minutes and no single spot on the 

 sea floor can be kept in view during that time. When the battery 

 supply is exhausted, after she has been at the bottom for 4 or 5 hours, 

 ballast is released and she ascends to the surface. Once the Trieste is 

 at the surface it is necessary to check out all equipment, recharge bat- 

 teries, and load ballast before she can make another dive. One dive 

 per day is her maximum capability under good weather conditions in 

 this area. 



Trieste made two series of five dives each in connection with the 

 Thresher search. Because of navigational difficulties and minor mal- 

 functions of equipment, only two out of each five dives were highly 



