1603. Submarines – Stability and Equilibrium

Paper

Abstract

Although submarines have been in use for years, many operators and those not intimately involved with stability and equilibrium do not appreciate and fully understand the need for weight control measures necessary to ensure that stability and equilibrium are maintained.
Based on many years of experience, it has been learned that many commanding officers of submarines do not want lead ballast adjustments made after successful sea trials in which no difficulties were encountered with diving and controlling their vessel. However, this successful dive is based on only one particular load condition. For the submarine to be effective it must be able to successfully operate in numerous conditions of loading. This often necessitates the adjustment of lead ballast based on the successful dive that the submarine’s operators have witnessed.
Part of this lack of understanding and hesitancy to concur with re-ballasting requirements is because the operators are not aware of the various evolutions that the ship yards are required to perform to ensure that the ship is properly ballasted for sea trials and then for delivery.
In order to provide a basis for dealing with the situation described above, a brief discussion of the evolutions the ship yards are required to perform, along with definitions and examples, is necessary. The topics to be discussed are stability, inclining experiment, submerged displacement, diving trim, equilibrium polygon, load to submerge, trim dive, and weight and moment.