Balast Tank

The main problem of submarine is the ballast tank. This unique system will drive the submarine to submerged and afloat. The question is: 1. The best structure of Ballast Tank i found a few solution in our research.

the first one, piston system:

this system been use widely in toy submarine. the fluid used in the piston is turkey fat(slick oil) that act as an excellent pressure transmitter and has less air bubbles. next, the electric impeller pump

this pump used in wakeboard. but the cost is really high the balloon pump

this system were the experiment used to understand the Archimedes' Principal. This method has a really low cost but need an air pump to pump in air