pigs and the addition or subtraction of water ballast inside 

 the float. The water ballast in the gasoline tanks permits 

 varying the loading of TRIESTE to compensate for addition 

 or subtraction of large amounts of weight. For example, 

 if the float were full of gasoline and the craft in its light 

 load condition with no scientific equipment aboard other 

 than its basic instrumentation suit, the craft would require 

 a topside loading of several tons of ballast to enable it to 

 dive. This variable load arrangement allows the craft to 

 carry a wide range of external equipment for various opera- 

 tions. 



The diving procedure is simple. When the bathyscaph 

 has been cast loose from the towing vessel, the handling 

 crew and the pilot go aboard and rapidly go through the 

 predive checks. When these are satisfactorily completed, 

 the pilot and observer enter the sphere, closing the heavy 

 door behind them. When the topside handling crew receives 

 information from the men in the sphere that they are ready to 

 dive, the handling crew floods the entrance tube with water 

 and then floods the end tanks by opening the topside vents 

 at each end of the float. The entrance tube is flooded be- 

 cause it is of no use to the crew during the dive, while the 

 alternative of making it pressure -resistant would result in 

 a tremendous structural weight penalty. The flooded en- 

 trance tube actually acts as a third ballast tank. Upon 

 surfacing, the pilot can blow the water out of the entrance 

 tube by compressed air, and can let himself and the ob- 

 server out. 



With all three "tanks" flooded, the bathyscaph begins 

 its slow descent into the depths. As soon as it sinks be- 

 neath the surface, the spring-loaded breathing valve goes 

 into action and begins to admit sea water to the float as the 

 gasoline is compressed. The deeper it goes, the more sea 

 water flows into the float and the heavier it becomes. To 

 moderate the craft's speed, it is necessary in some fashion 

 to get rid of weight. It is not feasible to blow sea water out 

 of the end tanks because very high pressure air would be 

 required. One can imagine the size of the air bottles that 

 would be needed to blow the end tanks against an ambient 

 pressure of 8 tons per square inch! Therefore, the ballast 

 system employs the dropping of mass weights from two 

 ballast tubs located in recesses at the bottom of the float. 

 Each tub contains 8 tons of steel shot ballast, the same 

 material that is used in industrial establishments for scaling 

 steel, etc. The steel is hard and has good magnetic prop- 

 erties. At the bottom of each tub is a funnel-like orifice 

 surrounded by a coil winding. When the coil is electrically 



