OPERATIONAL PRINCIPLES OF TRIESTE 



The principle of the bathyscaph TRIESTE is basically 

 the same as that of a free balloon operating in air. The 

 two major assemblies of the bathyscaph, the float and the 

 sphere, are analogous to the balloon (gas bag) and the cabin 

 of the free balloon. The differences in construction of the 

 submersible and the airborne balloon arise only from the 

 different environments in which the vehicles operate. 



The balloon (float) of the bathyscaph is filled with a 

 buoyant substance that is considerably heavier than the 

 helium or hydrogen normally used in the aeronautical free 

 balloon. Because the bathyscaph has to function in an envi- 

 ronment where pressure increases with depth, the buoyant 

 substance must have low compressibility; thus, helium or 

 hydrogen are totally unsuitable. Also, the buoyant substance 

 must not add so much on-board weight that it would be 

 impossible to lift the craft out of water and, preferably, it 

 should be a liquid that can be pumped from the balloon casing. 

 The fluid used in TRIESTE and, for that matter, all bathy- 

 scaphs at present is aviation gasoline, a liquid with a specific 

 gravity of approximately 0. 7, which is readily obtainable 

 almost anywhere in the world and can be easily handled and 

 stored. 



With the gasoline removed, TRIESTE'S weight is a 

 manageable 50 tons; with the gasoline aboard, the craft 

 weighs some 150 tons. Because of its weight, even in the 

 unloaded (50 ton) condition, it is not feasible to transport 

 the craft to the diving site on shipboard as few ships have 

 sufficient lifting capacity. Instead, the craft must be towed 

 and, in fact, it must remain waterborne at all times when 

 it is operational. Therefore, the bathyscaph' s balloon was 

 made sausage- shaped to provide a streamlined body for 

 towing. If it were possible to take the craft to the diving 

 sit e on board a ship and there lower it into the water, a 

 spherical shape would provide better streamlining for the 

 diving operation. 



Since the bathyscaph must be towed at sea and moored 

 alongside piers in port, the rubberized fabric used for con- 

 struction of the conventional airborne balloon is not satis- 

 factory for its float. Instead, the float of TRIESTE is made 

 of thin steel (0. 2 inch thick), which provides a lightweight 

 but strong shell and prevents loss of its contents from abra- 

 sion against the pier or towing strain. 



