Prop-N211-044_InflatableSubSail

The fairwater sail or bridge fin is a totally undesirable appendage when viewed from any hydrodynamic or hydrostatic aspect or from any other aspect including stealth. It causes considerable drag high above the centerline axis which causes a bow-up pitching moment which, in turn, overrides the other hydrodynamic effects on the hull and so determines the settings required on the forward and after hydroplanes to allow the submarine to maintain a straight and level path. This fin can generate vortices which produce noise. When the submarine is heeled into a turn, the bridge fin causes lift which can result in a “snap-roll.” When surfaced, it is the single most visible and characteristic appendage of a submarines visible area well above the waterline which announces “submarine” to any observer. It also adds considerable weight topside which is the worst possible place. The only reason the appendage exists is because it is a convenient place to locate periscopes, antennas, snorkels, and a surface piloting or bridge position. In addition, the location of the control room underneath the bridge fin is dictated by the need to have the periscopes available there. at periscope depth, the top of the bridge fin is only a few feet underwater where wave motion can affect the stability of the submarine and where there is a risk of collision particularly in crowded coastal waters. The amount of space required by the periscopes also makes the control room much larger than would otherwise be necessary. A submarine without a sail would have inherent advantages in submerged operations over a design with a sail in the areas of speed, maneuverability, and acoustic stealth. However, a sail is required to safely operate a submarine in certain situations allowing manual line of site operations and maneuvers. A sail that can be deployed when needed but retracted and stowed in a stealthy configuration when not required is desirable. Federal-Fabrics-Fibers Inc. (3F) has been designing and fabricating novel inflatable structures for many years, and realizes this application is challenging, but achievable. This phase I proposal will address many of the critical design criteria for the IDSS application, and further the knowledge base related to a viable IDSS  through design, drawing, numerical modeling, and physical component testing. as we strive for a more agile submarine, with visible and acoustic stealth, increased speed and maneuverability.