ancy when dry. The tanks are designed to 

 withstand 1,000-psf wave slap with a safety 

 factor of 2. At 2,000-ft depth 50 percent of the 

 flooded tank can be blown for emergency 

 ascent only. Six free-flooding openings are in 

 the bottom of each tank and a solenoid- 

 operated vent valve is located on the top and 

 at the rear of each tank. To dive, the sole- 

 noids are activated and open the vent valves; 

 this allows water to enter the bottom and an 

 indicator light informs the operator when 

 the tanks are full. The valves shut at any 

 time the operator releases the vent switch. 

 With the MBT's fully flooded, the vehicle is 

 at approximate neutral buoyancy and addi- 



tional ballast causes it to descend. To blow 

 the tanks dry, high pressure air (2,844 psi) is 

 used and stored in six flasks mounted port 

 and starboard between the deck and MBT's. 

 Each side has a flask of 21-, 7- and 5-ft^ 

 capacity each holding 262, 125 and 88 pounds 

 of air, respectively. Each flask is piped 

 through its own hull valve, pressure gage 

 and control valve and then grouped near the 

 operator's console where they are mani- 

 folded together and fed through a single 

 pressure reducer (1,422 psi) for normal blow- 

 ing operations. In the event of an emer- 

 gency, the relief valve can be bypassed and 

 high pressure air (2,844 psi) fed directly to 



Fig 6 2 Mam ballast tanks of BEN FRANKLIN straddle its pressure tiull Cylinder between sail and IVIBT tiolds compressed air to blow water ballast (Grumman Aerospace Corp ) 



289 



