LEEAMITe's Systems

Main Ballast System

This system has the function of creating negative/positive buoyancy for the purpose of destroying reserve displacement on diving, restoring it on surfacing, and, in some designs, creating an upward motivating force to initiate ascent. Consequently the design of the main ballast system is related to reserve displacement requirements regarding freeboard, the height of the access hatch above the waterline, and the provision for some small measure of protection against flooding. Design factors considered at this point include the volume of main ballast water and the relation between the longitudinal centers of main ballast water and reserve displacement.

The volume of main ballast, VMB, is given by the expression:

VMB = VMBT - VRW - VSTR - VI

VMBT = gross volume of main ballast tanks
VRW = is the volume of residual water
VSTR = water-excluding volumes of structure in the tank
VI = volume of any items housed inside tank

In this calculation, it is presumed that residual water, as previously defined, exists to a certain level in the main ballast tanks.

Since the specific weights of main ballast water and water in which the submersible is floating are equal, knowing the volume of reserve displacement requirements permits calculation of VMB and VMBT.

Main ballast tanks are almost always located outside the submersible's pressure hull. Their dimensions and internal subdivision, if used, should be such as to minimize free surface effects during diving/surfacing to the extent feasible.

Syntactic Foam

References

1. Allmendinger, E. E. Submersible Vehicle Systems Design. The Society of Naval Architects and Marine Engineers. N.J. 1990.